Saying Mata is a CM is very disingenuous. Mata could never play CM. He is an attacking player.
He's not a striker though. He's a non-defending midfielder like Kagawa, another expensive buy that has failed to pan out. And Herrera for that matter, his defensive work doesn't look real impressive either.
Fellaini, for the price we paid, was a bad buy. He is a squad player given his technique and control, but could do a job if we are chasing a game and cause havoc with his size. Basically, I'd lump him on the bench and use him as a super sub when I needed a goal.
Say that now, but when he was bought it didn't look so obvious. It looked like they overpaid, but for a useful player. Turns out they vastly overpaid for a player that did almost nothing.
As for...
Again, your argument started by saying the squad that Moyes took over was weak. If you wish to change that to the squad we now have is weak, I would be much more likely to agree with.
Both are true. If they weren't, then Van Gaal would just be taking last year as a one off under a bad manager and focusing on getting that sterling talent back up to its potential. He's not. He's bringing in players to try to replace those that were found to be not good enough.
Also, Vidic is basically on record saying he regrets signing with Inter so hastily, but he figured Moyes was coming back and that's why he left. So Moyes again shoulders some of the blame for our defense looking weaker now than when he took over.
Not sure why this matters. 50 league appearances the last 3 years, nearly 33 years old. Seems like he was past being good enough to invest significantly in anyway.
We've needed midfield reinforcements for ages. Sir Alex Ferguson made a big mistake by never addressing that glaring need. LvG is fixing it this summer, and I'm thankful for that.