I think most would agree, the players are as big, if not bigger (for me, a bigger issue) an issue as the manager - A lot of these players do need to go, and yeah we need those additions in defence and defensive midfield. While Ten Hag has dealt well with a lot of issues correctly, I do think that if his team doesn't have the legs to play the transition football he wants to play, he should have the ability to be a bit more pragmatic and just get the wins (However scrappy they are) against the likes of Burnley, Bournemouth, etc. I have no issues with his man management, I believe he's done that aspect better than Mou, Ole and LVG - I don't think someone like Tuchel will do better in that respect.
I do take issue with his tactics in these easy games he should win, yes of course we've got injuries but we can still win these games if we play with a bit more solidity after we've taken a lead - and I believe that can be coached. I would be OK if he gets a bit more time with a fully fit squad and a couple of additions in the summer to see if he fixes these issues, but I would also be OK with someone like Nagelsmann or Enrique coming in at the end of the season, as long as it's a tactically better coach that doesn't have a prolonged history of falling out with players.
Not going to put some of these transfers solely on the manager, and yes of course we'd play better with our injured players back / if we had better players in certain areas - But we should still be getting past these bottom half / championship teams despite these limitations, our 2nd eleven should be good enough to at least beat 10th in the PL. This is where he comes up short for me, and I hope he's able to address this if he stays next season.