Re: fixture pile ups, at a certain point, clubs have to take responsibility. The clubs worst affected by fixture schedules are the top clubs (competing in Europe, majority of players internationals). These teams have huge squads. Use them. It'd be easy to schedule each player a couple weeks off over the course of a season. Play more squad players and youth.
United alone, we have Henderson, Heaton, Dalot, Telles, Bailly, Tuanzebe, Williams, Garner, Laird, Van De Beek, Lingard, Diallo, Mata, Chong, Pellistri, Martial who have either barely played or been farmed out on loan. Not including Pogba, Cavani, Jones and Varane who have suffered injuries, or Matic who has played a small amount. Plus youngsters like Hannibal.