Certainly players matter. However, he had champions at Manchester United. He crashed and burned.
If Moyes was the manager some imagine him to be, he would have found himself at clubs with big resources more regularly in his career. In the manner of a top F1 driver, the best tend to get the best gigs. He got United, blew it, and was back to relative obscurity. Van Gaal, Mourinho, and Ten Hag also failed there - but all won trophies there too. Moyes won the Charity Shield.
I think he was harshly treated by United - but I never thought he had the skillset for such a job in the first place. His superpower was in spotting unfashionable players and turning them into very good performers. See Tim Cahill or Leighton Baines. That wasn't really the key attribute needed at United.
A good manager. Will do us this season. After that? If our resources expand - along with our horizons - we'll need a different skill set.