I think if it had XCX/Splatoon on launch, the Wii U would have been in a better place.

Because those are big games for the console, ofc if they had those at launch it would have been better off.

The problem is Nintendo.

They thought about function, but not about use, when designing the gamepad.

It should have been the game developement goal to make clear why they had those new functions in the console, and it should have come out big with all the launch titles.

(you dont design something, and then lateron figour out what to do with it, its assbackwards)

Instead everyone is like:

Why this gamepad? its heavy and not as comfortable to use as a normal controller. Its expensive and drives up the cost of the console for no reason.

If they had launched it with games that made really good usage of it (all of their launch titles), perception of the controller and the console would have been much better.

Launching with Mario Kart and Zelda would have had a greater impact than those games combined. Perhaps they should have added Toad as spare to show what the gamepad is really capable off. Mario Maker could easily be done without it ala LBP.

Then it would be similar, because it's not only about the games at launch..

Your question is wrong
İt has to be : what if wii u launched with 2015 hardware

It'd make little difference as not many people knew the Wii U was a new console or was even out, the same still holds true right now.

Not at all, I am fully aware of its deep deep flaws. I'm also aware of its good intentions, and I find it interesting how the titles this year show its value. 

I said nothing of the sort. Read and comprehend before you make comments.

I guess you could kinda say this about anything though.

What if the GameCube launched with Resident Evil 4 and had Twilight Princess instead of Wind Waker early in its life cycle.

That's the whole trick in making a successful console, it's all about making the right decisions years before the console has even come out and green lighting the right games earlier, so they can be finished earlier in the life cycle.

"Kart and Smash were both on Wii.  They don't do it.  They are derivative, which Wii U could not afford to be." 

You said Mario Kart 8 and Smash Bros. (both released in 2014) would come on Wii instead of Wii U.
This made me thought that Wii U would release in 2015. 

I don't think it would change anything.  The launch line-up isn't the main reason Wii U has failed to entice gamers. Rayman's delay was a big loss for Nintendo. But they had ZombiU which is one of the best game that uses the gamepad in a meaningful way. Overall was an ok line-up. Not great, not bad.