This is true, but you should be aware that the reverse is true as well....when they get a good coach, a lot of those poor signings will start to look like great players. Just look at Lukaku this season, he's absolutely brilliant playing for Conte and it's hard to believe it's the same guy who couldn't trap a bag of cement last season.
Solksjaer will never take them anywhere, but with Maguire, Wan-Bissaka now Bruno Fernandes if he comes, he is putting together some pieces that a good manager will be able to turn into a good side.
For all his faults (and I've criticised him a lot in this thread from the day he took over) I think he's been good for Rasford as well, he seems to be maturing into a real striker instead of the kid who wasn't a winger or a striker and only scored 6 goals a season.
So while he's a shit manager, he's probably going to leave them with half a team for Pochettino or whoever to make into challengers, which is a lot more than his predecessor managed.