One issue is three of those are best used (or any use) on the right. Then add that none of our wingers can do what Valencia can when he does perform. Unfortunately, Valencia's one-footedness doesn't only mean Nani moving left to coexist but also that the scope for wing-swapping is gone (which is one upside for Nani to pair up with Welbeck or Kagawa once fit). That also works against Zaha getting much gametime and will result in Januzaj getting the lion's share of the available minutes to blood youngsters.
I think both the Nani lovers and haters are way OTT here. He should probably be starting most games if fit, but there are clear cases where Valencia on the right or Welbeck on the left would be preferable.
It's the persistence with Young that I find bizarre, can't see how he can realistically start ahead of Welbeck if we want workrate (or effectively Hernández upfront on Sunday), or Nani (and Kagawa once he gets closer to fitness) if we want some creativity and flair.
If you look at rotation considerations I would much rather use the gametime towards Januzaj's development, let alone free up some for Zaha at all.
Basically, he is a backup and shouldn't even be on the matchday squad when everyone is fit. And no, I have no beef with him nor will I call him pathetic, I just don't see the point at all considering the other options available.