We need a multi pronged approach.
1. We need a DoF, someone who is tasked with maintaining the footballing footprint of the club. What style of football we want to play, what our plans are for success on the pitch.
2. We need to hire an attacking manager with the right experience. Age and years in the job count, but what we really need is someone who also can handle egos and can play attacking football.
3. We need to look at the squad sensibly. We do not have a terrible squad. If you said to someone in 2015/16 our team would have Sanchez, Pogba, Lukaku, Matic, DDG in it, they'd rate it very highly. The players might have aged a bit, but they've not turned dogshite overnight. It's the system of players/tactics/manager combined that is not working.
In my opinion;
Sanchez, Pogba and DDG are world class players in our squad (maybe not on current form). If we put them up for sale, all the big clubs would be interested.
Below them we have Lukaku, Matic, Smalling, who are good players in our league and if they were put on sale, teams with interest from CL quality teams.
Then we have some potentially world class talents who are currently good players and could be amongst the very best if they hit their potential. These are Rashford, Martial, Shaw, Dalot, Periera, (maybe Lindelof).
We also have some good squad players (Valencia, Young, Lingard, Fred, Bailly, Fellaini, Hererra, Maybe Mata) albeit some of them are aging and it shows.
The rest of our players are either terrible or limited (Darmain, Jones, Rojo).
You might not agree on the categorisation of each player, but you'll agree it's not all that bad, it's a team which is severely under performing.
With the right manager we could get better performances from what we have, but also we need to replace the limited players and some of the squad players with much better players. Our squad lacks a RW for example.
We are no longer at all change stage, but we do need some change in the squad, the right type of change. I think with an attack minded manager, if we add a world class CB and RW, we'd have a different team altogether.
It might well be that this happens and we need to replace Pogba or Sanchez or whever anyway because they're still stinking the place up, but I think we should try with changes at the top first.