Lol what good is having even 1000x more RAM if you can't ever use it. As a developer you would be more concerned with the speed than anything else. What good is having a 16 lane freeway when the speedlimit is only 35mph. I'd rather have a 4 lane highway running @ 70 mph so you can get all those cars home faster.
Lets review the Wii U's system specs vs PS3/Xbox 360:
You say that the Wii U has "much better stronger GPU" but that is just plain wrong. We live in a world where the PS4 having a 50% power advantage is labeled as just "marginally" better. And I will even admit that I was wrong when I said that the Wii U's GPU was only 50% more powerful....
So being that the PS4 difference is seen as "not noticeable" and "marginal" there is no way one can honestly say that the Wii U is seen as having a "much better stronger GPU" than the PS3/Xbox 360.
Combine the slightly better GPU with the slower RAM and slower CPU it is not surprising why many devs did not care to develop games for the Wii U. Hopefully Nintendo can do better this time around.
Even Wii U CPU is weak on paper, if its used on right way (use of huge and very fast EDRAM section and the big CPU caches in the cores) it can punche well above own height, just look how Nintendo used it for its game, most of Nintendo games working 720p/60Fps. Shin'en wrote how to use most of Wii U CPU and whole hardware.
So no, Wii U CPU is not 50% weaker than PS3/Xbox360. About GPU, its not just about power, Wii U GPU is several generations newer GPU than Xbox360/PS3 and that "allows many things that were not possible on PS3/Xbox360 consoles".
At end we have: somehow slower CPU and RAM but stronger and much more modern GPU and 2.4x more RAM. So similar performance like Xbox 360/PS3, but if hardware is used on right way it can have pretty impressive results for that hardware.
Nintendo made great hardware in Wii U for what they were aiming, very efficient, small, silent and in same time very capable 720p console, even if we know that aim wasn't good decision. I don't think they will use same philosophy this time again.