All of Canons 50mm lenses lack something, maybe except for the 1.2L (which is in turn quite expensive).
The 1.4 is built way under par, and the dramatic difference between image center and corners makes it
easy to hate it. The 1.8 is an insult in its build quality, and the optically well performing 2.5 compact macro
is in desperate need of a better drive.
So yes, there is a lot of need for a new 50mm.
I still have a 1.8/50mm MkI, and I have the 2.5/50 compact macro.
The 1.8 is good enough for low light, and the 2.5 is good for general work.
Both are way from perfect.
1.8/50 with the mechanical build quality of the 1.2L at a price point of 350 USD or below would be a no-brainer.
Let's see what canon comes up with.