In terms of hardware and architecture, The WiiU was much more powerful than the PS360. Four times the ram (2GBs vs 512MBs), much newer GPU with GPGPU capabilities and, for the time, modern shaders and lighting effects, more stable CPU. The issue came down to clock speeds. The CPU of the WiiU was down at 1.24GHz while the PS360 CPUs were up in the 3GHz range. This would mean the rest of the hardware was slow and developers at the time would mention how slow the RAM was, regardless of there being four times as much. Imagine a game that was programmed to run on hardware that was 3 times faster than what it's being ported to. Suddenly that game would run much worse. Wouldn't matter if the other hardware could run more complex code more stable than the previous hardware, the game wasn't using that code to begin with. Doesn't matter if there is more memory if the game was never programmed with that much memory in mind. That low clock speed caused a lot of issues with ports that you wouldn't see on games with either dedicated versions or games made specifically for the WiiU.
Wii U have a weaker GPU than Xbox 360 and a weaker CPU than PS3. This have nothing to do with vram. You guys are so focused into the specs that forget Nintendo was criticized for not having the basics back in time. Don't matter what their GPU can do in comparison with the competition if their advantages only stick on the paper.
Nintendo gaming API was less efficient than even the PS3. Of all consoles of that generation, PS3 have the stronger CPU, but thats not mean is less problematic. Devs got a hard time coding games using the PS3 CELL architecture.
Thats why devs are right now exploring what Nintendo Switch can do, because even having lower configuration than PS4/Xbox One, they are extracting much more with an improved gaming API.
I ask you guys to rewatch all Digital Foundry videos in this matter. For example, Digital Foundry Resident Evil 5 port. Even Nvidia Shield having similar specs of better than Nintendo Switch, RE5 runs poorly in comparison with Nintendo Switch.
Another great video I would recommend is the Digital Foundry Wii U launch presentation.
How you fit 2 GB of RAM + 32 MB of eDRAM into 512 (or 256 + 256) MB of RAM?
Can't say about what devs can or not with the amount of power given, but third party games do runs worst on Wii U in comparison with PS3 and Xbox 360. Assasin Creed, Batman AC, Call of Duty... you name it.
Remember, PS4 have 8GB GDDR5 and devs are saying is already outdated or not enough for today standarts.