I think you significantly underestimate the damage Moyes did with his completely defeatist approach, clueless appointments and general sourness. That meant LVG had to pick up the pieces. Something Jose is still in the process of doing (and very well I may add), as well as fixing what LVG did, which was to compound the misery by telling the players not to be themselves, whatever they do.
It was one season. Teams have bad seasons. Finished 7th and were out of the CL, then the following year, we were back in it. Chelsea finished 15th last season and may win the title this one. It's too easy to blame Moyes.
You go on like Moyes changed the whole team. He made four signings, two of which who were main stays under Van Gaal and still under Mourinho - those players being Mata and Fellaini. I'd also like to add that, although Herrera was signed under Van Gaal, Moyes made that happen. Same applies to Shaw.
I just think there's a lot of people who like to be over dramatic when it comes to Moyes. He was poor, and was rightly sacked, but it really isn't as bad as some make out.
If anything, having Van Gaal, especially for two seasons, was much more detrimental to our team than Moyes.
1) His style of play was a style we're not used to, i.e. slow build up, organised, possession, etc, whereas at least Moyes had a similar approach to Sir Alex, i.e. getting it wide, crosses, counter.
2) He also had the players like 'robots' using the quote from Schneiderlin, which, as you said, meant the players couldn't be themselves.
3) Made rash decisions and got rid of players who could still be very useful today, i.e. Welbeck, Keane, Hernandez.
4) Signings didn't work. Di Maria, Schneiderlin, Schweinstieger, Darmian, Depay, Valdes and Falcao turned out to be poor signings by Van Gaal.
Having said that, like I said, I still believe we have a good enough team to be challenging for the title, and had it not been for all those draws, we would be. It's all too easy to blame it on past managers.