Few of them are ports of Wii U namely MK8 and Pokken tournament...oh and BOTW as well.
The reason that the Wii U didn't have the games that they were suppose to have is because of two things I could think off.
1. Either because the Wii U failed so badly that even if Mario couldn't save it, then its not worth for Nintendo to release games for a failing system when they can instead waste that amount on the next console making the hype games for that system in this case the Switch.
2. Because the devs weren't able to do enough for the games for the Wii U and so decided to make their games on the Switch instead.
And also, its not like most of those games are on high in demand. Arms is just as good as Splatoon was when it was on the Wii U. And again, it has the same issues as Splatoon namely that its not more of single player.
Then Xenoblade Chronicles 2. Ok...again, the Wii U had X so there's not much of difference and that X is more well received than 2 so another plus for the Wii U.
Mario X Rabbids...no one saw that coming and its a crossover nonetheless so again, not a game in such high demand unless you're a fan in strategy games. Also, a game by Ubisoft of all that alone says it all.
Warriors is a game that was also on 3DS so its not like its a major game that sold well btw.
Anyways, all of this is exactly the main reason why marketing for the Wii U IS the reason why the Wii U flopped. They couldn't even market the best games that the Wii U had properly on par with the level of the games for the Switch. The line up for the Switch despite having somewhat of a better library of games early on is still no better than the Wii U because
1. Few of the games the Switch has are just ports of the Wii U games like BOTW.
2. Most of those games aren't like "universal" acclaim. Examples are Xenoblade Chronicles 2, Fire Emblem Warriors, Mario X Rabbids. They may be worthwhile games yes but as far as quality goes, they are nowhere better than the games the Wii U had like Xenoblade X, Tokyo Mirage Sessions(can't believe I said that...) and Mario Ultra tennis I think it was called for the Wii U.
3. The amount of devs that hesitated to make games for the Wii U are on par with that for the Switch. I mean, seriously, even with the Switch sales booming, there's no way we're getting final fantasy 15 or Secret of Mana for the Switch.
But all that is going to change because the Switch's marketing is about twice better than the one that the Wii U wished it had. I mean...MARIO CEREAL?!?!?