The point is, as average as you say they are they still outperform the players who will remain by a large margin.
Lukaku scores goals despite not looking good enough. Pogba creates and scores, despite not looking like he gives a shit.
These players will move on to clubs who are competing for trophies while we keep hold of the likes of Matic, Mata, Lingard, Young, Jones, Smalling etc and then fans wonder why we don't improve or get any better.
If we fill the squad with players just have the right character or want to play for the shirt then you get a list of players just like the ones who are going to be stuck here, right attitude but shit otherwise.
I agree to a degree with a lot of what you are saying. The thing is, they havent been good enough, certainly consistently and like it or not, the fact is they have been our two biggest transfer deals, by some margin as well.....so theoretically they are also our two most valuable players. Selling those two brings in £200m, if we were to sell the six players you mentioned we are talking probably £100m.
Its putting a lot of pressure on his shoulders but considering how poor Lukaku has been for a while (I have never rated or wanted him personally anyway) and the fact that it appears he is the second choice striker for Ole.....does he even need replacing when we have Greenwood? That leaves £200m to buy three new midfield players, replacing Fellaini, Herrera and Pogba.
£100m coming in from the other sales and we would need a central midfielder, right winger and centre back at the very least to replace those six.
Personally I would happily sell Pogba, Lukaku, Matic, Young, Jones and release Mata all this summer from the players you mention, along with Sanchez, Rojo, Darmian.
There are several others of course, but I think we need to get rid of the main deadwood and players of value. Even if this was football manager there is too much out and in to do in one window sadly and even what I suggest is barely realistic in one window