The only permanent solution to Manchester United's squad would be to replace Ten Haag. Because he's been around for a long time and friendly behavior has weakened, players will only perform better if he's down. Although players may not develop a passion for the Manchester United team, it is possible to do so. Because Ten Haag's behavior is not obvious to the players, there are weaknesses, so from different angles I can understand and this will be a permanent solution. Manchester United team will perform well only if Ten Haag is replaced by a new experienced coach.
I also have an opinion that is not much different from what you said for Manchester United, because a team as big as Manchester United should be able to have a coach who has a lot of experience and tactics that he can apply to every player in the team. Not just buying players as he wants, then he just guards them without giving them good tactics in every match because in the Premier League almost all teams can be stronger if one of them plays without relying on tactics and better finishing in every match.
If only Erik ten Hag did not succeed in making Manchester United get the FA Cup trophy last season, it seems certain that Manchester United has a new manager this season. Or maybe, Pep Guardiola deliberately let Manchester United win because withthat result, Manchester United proved to give Erik ten Hag another chance this season. But anyway, the fact is that many Manchester United fans really want Erik ten Hag to be fired and indeed, it seems to be a good solution to restore Manchester United.
But it seems, if maybe later Manchester United appoint a new coach but the coach needs adaptation, then the results will still be just as bad. With that reason and maybe, by appointing a coach who already has great experience and is familiar with the Premier League competition, then it could be fast for the new coach to be able to restore Manchester United.