I think we over look how important it is for a player to be playing in the correct tactical style. For example, Bruno's best form for United and Sporting is when he has freedom, in and around the no 10 role. Take him out of there and he doesn't have the quality to be effective. If Rashford is not playing on the left with freedom to not track and loads of space he becomes ineffective. No surprise both players best form came in a 4 2 3 1 where the team was much more defensively solid to allow for that. Alternatively, Sancho flourishes with a fluid interplaying style, the opposite of what United played with their 4 2 3 1. The result is he doesn't look anywhere close to the player he was at Dortmund. We see this all the time, certain players need certain formations/playing styles to get the best out of them. Additionally that also means managers with certain play styles need certain profile of players. I think this is why you see a player fail at 1 club then succeed at another, and same with managers. This becomes even more important the tougher the league is. Its why for example, I don't think Ten Hag was a bad manager, far from it (however I do think he was bad at recruiting the right profile of player).
The reality is a large section of our squad are not bad players. As much as I'd have moved Maguire on, if we had kept Jose I'd see him doing well, as I think AWB would have done due to the more defensive style. What we are seeing right now at United is the extreme of a squad of players that are not suited to Amorim's style. Maybe in time with coaching they will become suited but that is not a guarantee. Add to that the point that the squad must be low in confidence (there is no way they can't be after last season and the start to this) then things get amplified.
I personally do think the correct course of action is a reset. That being to pick a philosophy/style and stick to it for a period of time. If that's Amorim so be it. However, what has hamstrung the club is the need for success within 2/3 years and the need to have stars to increase the commercial side. That doesn't work when ideally you need to sell Bruno and Rashford your biggest stars (my opiniom they have to be moved on). It also doesn't work when you need success to sign players, keep top players etc. It's a tough position the club finds itself it, a lot of pressure on Amorim.