Just because some people didn't like particular plot developments doesn't mean the series was "derailed." Star Wars wasn't hurt any more by the sequels than by the prequels, which also had copious amounts of fan rage directed at it. And Star Wars wasn't "desecrated," either, because it was never sacred in the first place. They're movies! They're meant to be entertainment, not a religious experience. Star Wars fans saying "The franchise has been desecrated!" or "My childhood was ruined!" is not constructive criticism or part of a healthy discourse. It's just unwarranted negative hyperbole over the filmmaker's creative vision clashing with their own personal opinion of what Star Wars, its characters, etc., are "supposed" to be (also, a non-trivial portion of the complaints over the Disney-era films are simply political natter; just so we're clear, please note that I'm not saying your comments fall under this category, but rather I'm just pointing out its existence online). You may have personally not liked the sequels, but that does not mean Star Wars was somehow mistreated by its current owners and managers.
I've enjoyed Star Wars ever since I was a kid. I grew up with the original versions of the original trilogy. I had plenty of issues with the Special Editions and the prequels, many of which are common complaints. But I've never felt legitimately outraged over those things. I never felt the urge to go on the internet and use every opportunity to rant and rave about my childhood being ruined (because it wasn't). I didn't hold a years-long grudge against the directors or producers. I was mildly annoyed and quickly got over it. I still enjoyed the prequels enough to watch them each twice in theaters, and I've re-watched them on home video and TV numerous times. I did and still do regard them as entertaining, warts and all. A decade later, latter-half-of-my-30s me enjoyed the hell out of all the new movies. I view them as having better acting, direction, cinematography, etc., than the prequels. They were fun, funny, and exciting, with more "this is awesome!" moments. As individual works of film, I like the sequels better than the prequels. I do think the prequels were more cohesive as a group (having a single person with total creative control helped) and did better with world-building, but as films they left a lot to be desired. George Lucas is the kind of filmmaker that works best within boundaries, and probably shouldn't have been sitting in the director's chair (which he wasn't for Empire and Return).
As a whole, I take the franchise for what it is: A fantasy film series about laser sword-wielding space wizards and ragtag rebels fighting evil empires. It was never meant to be anything highbrow. It was meant to entertain and make money, and that's it. And in that regard, it is a success for me. I enjoy the hell out of Star Wars. It's kept me entertained for decades. I watch all the movies on a fairly regular basis. I even still get goosebumps when I hear the theme. But my life doesn't revolve around it. I understand that it does not belong to me but to the owners of the copyright. And I don't take it personally when the owners do something that I don't like. Same goes for anything else I'm a fan of. For example, I'm a Halo fan, and I have had plenty of objections to various changes made to the series over the years. But I try to be constructive over it, and I've never once claimed that such and such change ruined the franchise.
As for toys, based on what I could find (solid revenue or sales figures are scarce. esp. to compare anything recent to prequel-era or 80s/90s sales), shipments were already down well before TLJ was released and angered some fans. Rogue One, despite being well-received and being the follow-up to the also well-received The Force Awakens, saw a huge drop off in toy sales as well. Unless the only people buying action figures in the past were the relative few that also hated TFA, then there's something else going on besides fan outrage.
Also, why are toy sales being held to such a high standard as a barometer of the series' continued viability? What about the video games? Despite the additional controversies over loot boxes in Battlefront II, Star Wars games are selling better than ever under EA. Fallen Order is apparently already the second best-selling Star Wars ever, at least in the U.S. And what about the movies themselves? As I already mentioned, the box office figures showed that Star Wars is still healthy as a film series (Solo doing relatively poorly notwithstanding). Domestically and adjusted for ticket price inflation, TFA is the highest-grossing movie this century and fifth-highest since 1975, while TLJ & TRoS pulled in approximately 14% more total ticket sales combined than AotC & RotS and placed #7 and #13 among all films released in the 2010s. And as I mentioned The Mandalorian is a big hit.
If everything but the toys is doing well, then maybe that says less about Star Wars' current state as a franchise than it does about changes in the toy market in general.
Also, what do you mean "most fans"? There's obviously never been a survey of the whole fanbase to make such an assertion. The best we have to go by are review aggregators. Ignoring the instances of obvious review bombing on RT (before the policy changes) and Metacritic, the sequels were not received any worse than the prequels. On IMDB, in terms of percent of people giving them good reviews (at least a 7/10), the sequels fare better than the prequels, with TFA being better-received than any of the prequels, and TLJ and TRoS faring better than TPM and AotC. In terms of average score (especially after eliminating 1/10 scores, because they're obviously issued in bad faith), Episode 7 has the fourth-highest rating in the series, bested only by the original trilogy films, and Episodes 8 & 9 fare better than Episodes 1 & 2. And there's not a huge gap between even the sequels and the originals, either. Again excluding the 1/10 scores, there's a less than 1.5-point gap between Rise of Skywalker, the least well-received of the sequels, and Empire, the best-reviewed film in the series. Letterboxd shows the same basic thing as IMDB does, with the sequel trilogy being better-received overall than the prequel trilogy. (I can provide charts visualizing the IMDB data upon request; I have the data, but I haven't yet taken time to make .png files out of the charts)
There is no evidence that the sequel trilogy, or any specific film in it, is somehow more hated than the prequels by audiences writ large. There may be some people that really, really hate them, but the vast majority of people think they're okay to good. The prevalence of fan outrage on the internet is rarely indicative of a general consensus that the object of controversy is actually bad, much less a sign of looming trouble for a franchise (see also Pokemon S&S already on the verge of being the best-selling entry in its series in 20 years despite the fan outrage over a pared-back Pokedex; said outrage predictably resulted in review bombing on Metacritic, which is apparently just what some people do these days to say "I'm mad!"). There's a reason why I keep using the term "vocal minority." Because that's what the evidence suggests it is.
People are more accepting of the prequels nowadays because of chronological distance and the nostalgia filter. Most of the anger over the prequels came from people who grew up with just the originals, and I imagine that since the prequel trilogy ended 15 years ago tempers have cooled down. Those who were kids when the prequels were new and that grew up with those movies seem to have a greater appreciation for them, but now that they were adults or older teens when The Force Awakens debuted, many of those who hate the sequel trilogy come from from their age group (and maybe some of the older fans).
People are always going to be far less critical of and more attached to things they grew up with as kids. Children are not film critics. They are more easily entertained. And when they grow up, they often get nostalgic over things from their youth, even if that older thing actually wasn't very good in retrospect. This nostalgia sometimes leads them to develop a sense of ownership over the property and an idea that any new additions to the property have to have certain attributes and not others. Any perceived deviation from that idealized conception results in some fans feeling that their long-time support has been somehow betrayed, and they react with anger. The newer material is deemed as not living up to the old-school stuff at best and heretical at worst, regardless of the actual quality of either the old or the new works. We see this "RUINED FOREVER!" reaction with all sorts of fandoms. That phrase was actually coined in relation to the fandom of The Transformers, another franchise I grew up with. A lot of other older fans of the franchise are G1 purists, with the original series being the bar by which every new entry is measured. Even though the original series was not even close to what anyone could consider a masterclass in TV animation, many older fans treat it as sacred. It's something we see with many, many franchises. Because nostalgia is a hell of a drug.
And I imagine this will be a cyclical thing with Star Wars. The children of today who are growing up with the sequel trilogy are in 10-15 years' time probably going to look back at the adventures of Rey, Finn, and Poe with wistful nostalgia, and older fans who hated the sequels will probably (hopefully) have moved on. But whatever new Star Wars films may or may not be released at that point in time will probably elicit disappointment, anger, and even rage from the children of today for not meeting their expectations as adults with feelings of nostalgia.
Star Wars toy sales have been struggling for a long time, really since Episode I in 1999 fizzled and lots of retailers were left with unsold crap.
Hasbro never made money off the Star Wars toys even during the prequel era:
"No doubt 'Star Wars' is an important property for Hasbro but the history of that license hasn't been overall profitable for them," said Timothy Conder, analyst with A.G. Edwards. The company struggled with sales of Star Wars toys in 1999 after Hasbro originally paid about $590 million for the exclusive worldwide rights.
What really happened is The Force Awakens is an outlier that saw a huge surge in spending, and things have basically gone back to the same decline as before.
Action figures are simply not the staple for kids these days.