That's not true for third party games on the Wii U. There are plenty of good games that sold terribly on the Wii U . 

Engines are scalable, your second point is entirely moot.

Of course he is right about Just Dance. That's why WiiU users are generally slimmer, more fit and have better dance moves than owners of other consoles, damn lazy slobs.
Microsoft tried to get their gamers in shape by gifting them Kinect out of the box, but faced huge backlash from it. Now they unfortunatelly bundle XOne with free fajitas and nachos.

Rayman Legends sold 360k. ACIV sold... 190k. More importantly, its cheaper to port a game like Rayman Legends to Wii U versus a AAA game like ACIV.

Furthermore, lets not forget CoD:Ghosts sold a measly 170k. Splinter Cell sold 70k, Deus Ex sold 50k, etc. Numbers like that aren't worthwhile.

Watchdogs on PS4 has sold more units than Wii U has sold M rated games. That game has only been out for a few months, Wii U has had M rated games for about a couple years.

Why not port Rogue instead of Unity?

It's not 100% accurate no, but often it will take a game or two for people to make it worth while to spend money on. Wonderful 101(second party) is a good game but hasn't sold great, Shovel Knight has. Big difference between the two is that Shove Knight has had a lot more attention drawn to it in comparison. Problem with AC3/4 is that neither are great games, especially 3 and some people took a chance and it didn't pay off for it.

The other side of it is that many of the good games have been inferior ports. While Arkham City is a great game it isn't a great port, same can be said for Deus Ex. To go along with both of those, they are late ports meaning that they were released a long time after they were intially released on other consoles, any if not all of the hype has died down so they are actually aiming for a much smaller audience because of that. We won't know for sure, but it's possible that Watch Dogs might have sold quite well on Wii U if it were released at the same time as the others, but at this point it's quite likely it isn't because there is next to no hype or media attention, and the game only received mediocre/modest review scores.

Much of it does seem to be cause and affect. I think what might show how well they could have done is when Devils Third and Bayo 2 are relased on the system. It's possible that much of the audience doesn't want these kinda of games, but it could also be much of what I have said.

That's entirely untrue. If you want a direct instance of this feel free to use almost any PC game and use the highest graphics settings as opposed to the minimal settings. As long as the Wii U can run the API's that are necessary for the game to run, it should be able to run the game. Just because a system that is of lower power doesn't mean it's holding back the high end of the spectrum in the slightest. That is encompassed by the vast varianc of PC's. Many games can be run with on board, even the lower end versions, GPU or APU solutions and since much of their market is made up of that, it's necessary to develop for them. Also, contrary to popular belief, the Wii U is not as far behind the PS4 and X1 as many think it is. Admittedly when looking at the numbers it seems to fall behind, but when in comparison to the variance of PC none are powerful systems and the PS4 and X1 are only slightly more powerful than the Wii U.

Ubisoft:

The best way to build a fanbase is to give up

Took that long to figure out huh?

Is 360k impressive for Rayman Legends? Yeah, that's pretty good for a 2D platformer. It sold over a million in combined sales, its a hit.

Well clearly it takes more effort than you think to make a Wii U port. Otherwise the Wii U version of Watch Dogs would be here already.

If AC games were selling around 500K on Wii U, support would probably continue. But 190k for a game doing so well on other platforms is pathetic.

Bottomline, 3rd parties brought some huge IPs to Wii U and they were generally ignored.

The audience that wanted mature Wii games disappeared. CoD used to sell millions on Wii. Yet CoD:Ghosts is struggling to break 200k on Wii U. Try doing some research.