Can you explain why it is supposedly so difficult to develop games on the Wii U?

[Solid-Stark]

What I take from it, developers have problems due to ram and the cpu. Thought the cpu can do more per cycle compared to ps3 and x360, its slower, and lacks in overall power compared to ps4 and xone since they have more cores. Couple this with a fraction of the ram in comparison, engines are tougher to run.