Manchester united problem is something else because they have continued to change players and coaches since Fergie left the club but all to no avail. It's quite sad to witness a once giant of the game even at the world level to be so belittled by so many little teams because I believe if Manchester united were in good shape, crystal palace would never had won that game with such huge margin.
I understand your point and it's very valid for a team thst was seen as elites across Europe and beyond and now they are not even able to compete with average enough to winning them I think it's really a thing of concern because the decline has lasted longer than expected, unlike other top European teams who once experience decline they at some point later got better in their form and they later came back in their form.
Manchester united needs time and a Coach that will be able to help them build up the team once again and get them back to their glory days where they will be able to win games and possibly trophies as well, Manchester united has failed to be able to get this done and rather getting coach who are just wanting to win trophies even without trying to build a team that's capable of that with strategies thst will definitely get to work for them, even the players at some point do appear like they aren't playing to even win or get the team back on their form because they don't look good in their form.
Crystal palace is a team that shouldn't be a team that will defeat Manchester united in such a way that the margin is that big and they are now appearing too weak that they are not even going to qualify for the champions league and most likely Europa and I think nit will be very important that ten hag should be sacked and then get a good coach that will help this team to be able to build up and get back in form again.