They should learn from Star Trek and read up on what franchise fatigue is. Besides the issue of social justice injected into the franchise of course.

Did anyone do the comparison where Episode 2 made about 1/3 less than Episode 1?

It's not really fatigue, though.  Look at Marvel.  They are putting out 3 movies a year, now, yet it doesn't hurt them.  No, the problem is that TLJ divided half the audience.  Some liked it.  But, a lot also either thought it was meh or they actually hated it.  The latter crowd had no desire to watch it a 2nd or 3rd time, leading to a big drop from the expected $750M+ DBO and $1.7B+ WW take. 

There are a myriad of reasons people disliked it.  Mainly because of how they treated the characters/lore and how the story really amounted to nothing.  The main plot is a 8 hr snail race, which creates so many holes in logic its mind-boggling.  But, yea, the on the nose SJW messages were annoying to many, even those on the left.  Really an amateurish way to handle those messages.  Not to mention they have no right being in this franchise, which is meant for those of all ages and political leanings.

Star Wars has always been political, Lucas is about as left wing San Fransisco artist as it gets, lol, American Zoetrope was basically nothing but an artists conclave in San Fran for experimental filmmakers. The Emperor was originally conceived to a knock at Republican president Richard Nixon, the "Rebels" are basically the hippie/revolution counter-culture movement against the right wing military establishment. The Ewoks are also an analogy for the Vietcog fighting the American war machine. Lucas has said all this stuff himself. Revenge of the Sith also took clear shots at George W. Bush's invasion of Iraq.

As for toys ... no one plays with toys anymore, kids want iPads not action figures, the toy industry is basically just going to be 1 aisle in a Wal-Mart or Target, there's no market for plastic junk. The action figure/toy/doll market is dying and has been for a while, The Force Awakens just gave it a solid push because it was an event picture, spurred on by a decade long wait. 

Marvel has thousands of pre-existing character properties from 70+ years and thousands upon thousands of comic books, you can't really compare anything to Marvel other than DC. Marvel is not really meant to be some kind of singular universe, Marvel's philosophy was basically to make a comic book for anything kids of the time might want to read. So you have horror (Blade), sci-fi (Guardians of the Galaxy), mideval fantasy (Thor), mystical/magical (Dr. Strange) modern urban heroes (Spider-Man), etc. etc. in one universe, Marvel gave no fucks about if things really made sense or tied together when making up these characters, they needed to go home on a Friday and would just come up with some goofy thing they thought maybe 50 kids would like to see and that was the extent of the thought process behind it.

The result is franchise fatigue is not going to hit Marvel as hard because they have multiple genres they can tap into. Star Wars is basically only sci-fi/fantasy anyway you want to spin it.

Excuses, excuses, excuses.  And poor ones at that.

I suspect those are meanings he added later in his life, as the original was a homage to old Sci-Fi serials, just like Indiana Jones was a homage to action adventure serials.  Even if that is what he intended, they were written with such broad strokes that it wasn't slapping you over the head with its message and could be enjoyed by all.  The new one was incredibly amateurish.

No one plays with toys?  Lol, boy that's quite the excuse.  I guess the toy market has changed SO much from TFA and RO, which only came out 1-2 years before TLJ.  Come on, man.  And 1 aisle?  There's still like 6-8 aisles in every Walmart dedicated to toys.  Oh, and toy sales were actually up last year slightly, even with the poor performance of SW toys.

Marvel has so many genres?  Again, come on.  Marvel has a formula they follow for pretty much all of their films.  They also take great pains to make sure that most of them feel and look very similar.  The difference is they are making movies that don't piss off about half of their fans. 

Pretty telling that Black Panther, a standalone Marvel film, is going to easily pass TLJ at the DBO, and is going to either come incredibly close to it or even pass it WW.  Again, the movie where the safe bet was for it to enter the Top 3 (most likely #2) with $750M-$830M, and stay there for years/decades to come.  And make $1.7B-$1.8B WW, entering the Top 5 at #4, to stay there for years/decades to come.  Instead it won't enter the Top 5 DBO, and will be pushed to #7 by BP, with 2-3 years before it is pushed out of the Top 10.  And it is going to most likely top out at #9 WW, and could get pushed out of the Top 10 this year.

I'm not going to argue TLJ's reception, because it did burn a lot of people. (I do think it's weird to say the expectation was 750/1.7 - 700-750m domestically was totally doable, but that's expecting a pretty small drop internationally, especially when Rogue One showed Star Wars has no pull whatsoever in China - my prediction was 704/1.4, expecting the same 50/50 split RO had)

But toy-wise, where was the appeal? All of the heroes look exactly the same as they did in The Force Awakens. Why would you buy your kids new toys that look the same as the ones they already have?

(I wonder if Ep IX is going to have a ton of costume changes to try to rectify the toy issue)

RO is a spinoff.  Of course it's not going to have the same draw as a main installment of the franchise.  Though, as this thread shows, TLJ is suffering some extremely poor legs, as RO has been outperforming it overall for the past 2+ months.  Still, if anything, TFA shows that SW can have a decent draw from China.  It made $124.2M there, after a $52.3M opening, which is a 2.4x multiplier.  Obviously, the Chinese didn't exactly like TLJ, either.  It opened up lower than RO, with just $28.1M.  Even if it opened lower, if it still enjoyed the same multiplier, it should have made $67.4M.  Instead it was pulled out of theatres the next week, only making $42.6M.  If Disney was attempting to expand SW's popularity in China, TLJ was not the film to do it with.

BOM and movie analysts stated that TLJ was safely going to do $750M+ because of the fact it launched only 11.3% behind TFA.  It would have fallen down to 20% behind over the rest of its run to just make $750M.  No one really expected that kind of drop, which is why the range was given.  Most probably thought the max it was going to fall was ~15%-18%, which would have been ~$768.1M-796.2M, but left open the possibility of it doing even more if held. 

Same goes for WW,  TLJ opened 17.9% below TFA.  If it had held, it would have made ~$929M.  That's what gives you the range of ~$1.7B-1.8B.  What's very telling is that even after the large 2nd weekend drop, analysts thought that the film would still be able to hit $1.6B WW.

Ah, I was referring more to predictions before the film's release - most I saw were in the 675-750 zone.  I won't argue at all that a 220 OW pushed expectations up for how it should have finished.

You're absolutely right that TFA was not the film to launch the franchise with in China.  For a lot of these emerging markets - especially the ones that didn't have easy access to the OT, like China - these Disney-era films are confusing.  First you get a sequel that's heavily reliant on films you haven't seen, then a prequel with none of those characters, then a sequel to the first film, and then in a couple months another prequel with yet more new characters.  I'd be annoyed, too.  There's no rhyme or reason to it when you don't have the OT as a foundation.  The Marvel films, for as many as there are, are (generally) chronological and can be followed that way.

I do think it's a little silly to have expected TLJ to have matched TFA's legs - it's a sequel and will therefore be more frontloaded, as fans rush out even faster and people who didn't like TFA don't make up the difference.

I'm curious to see what IX does.  Revenge of the Sith bounced back from Attack of the Clones because of the finale factor.  I don't know if IX will get the same boost - even if it's marketed as the final episode, people know Star Wars isn't going away this time.

I don't think the problem was TFA, as it still did respectable numbers in China.  The problem was trying to expand the audience with TLJ.  Even though TFA wasn't perfect, it still has the same positive spirit as the OG trilogy, which Disney has been running on TVs in China.  TLJ was a more nihilistic take on the franchise, and it didn't sit well with many fans. 

Being a sequel doesn't necessarily mean it will do worse than the original.  Marvel has been building off each standalone installment, with the sequels doing better than the one before.  Of course, there was a lot of build up for TFA, so no one really expected TLJ to match it.  But, no one saw a drop as big as it had.  Again, you're putting too much emphasis on TFA.  You could say that those who disliked TFA caused a lower opening.  But, it was only 14.8% (-$78.1M) down opening weekend.  It's continued drop to being ~35.5% (-$733.2M) down rests completely on the shoulders of it being a good film or not.

ROTS got a boost due to it being a little bit better/darker film and also because it was the lead up to the creation of Darth Vader and the beginning of ANH.  Episode IX has a lot working against it.  Not only does it not have the most iconic villain in it, but it also follows an installment that turned a lot of fans away from future installments.  TLJ didn't really leave anything at the end to look forward to.  And even if it tries to retcon some things that happened in TLJ and/or address loose ends TFA left to be tied up in a sequel that TLJ ignored, it will just become a muddy mess of a film.  I won't be surprised if IX opens below $200M.  A first for the new SW trilogy.

TFA was hated in China, and that was reflected in the gross of Rogue One.  Remember, it's a new franchise to them, so they don't really see the Episode/Star Wars Story distinction that we do.  TFA made $124m, RO made $69m (despite the inclusion of Donnie Yen).  Two films in a row they didn't like.  I know you like using expectations as a gauge, and every single pre-release TLJ China prediction I saw had it dropping off even further from RO.  The franchise is simply a disappointment in that market - they gave TFA a chance, didn't like it, and so the next one flopped.  I don't say that to disparage TFA, as it's a film I like.

All I can ask is that you find me a massively anticipated film that opened to huge numbers and then had a sequel that stayed flat or grossed.  The only one I can think of that even stayed flat is The Hunger Games: Catching Fire.