I think the lack of CDM plays a big part in this. Fred/ Mctominay are not trusted on their own, they are not good enough.
I like the point of the Turkish team example because everyone I have seen posts how good we were in that game but we weren't any good defensively.
They kept getting chance after chance and I do not think Ole wants to go into games you attack we attack, he wants our team to have a solid base.
There is a couple of things with VDB that stands out at his career for United so far.
1) If Ole doesn't exactly value him as a player - why do we arguably see him most of the time when we need a goal in the last 10 mins of the match? Wasnt this a bit like how Ole himself was utelised, a bit like our super sub?
2) I think one of the most interesting things is how he has played in different positions so far as a Midfielder; he has played deep aswell as playing as the further CM forward in a CAM role.
3) he actually plays the game differently to the CM or CAM he competes with like Pogba, Fred or Bruno.
Do we have a CM who plays like VDB? Does he play like Pogba? Not really, from the little I've seen him from deep - he has almost been a possesion recycling player that keeps a tempo to our game by making short simple passes to the player in better position.
What about at CAM? VDB plays the role differently to Bruno Fernandes. Whilst Bruno Fernandes has great creativity almost to the point that he can play as a false 9 or CAM that brings others( mostly wider players) in to play - VDB is the opposite, his passing is more simple but makes runs like he is a shadow striker in to some deadly positions that are not really being picked up by someone else.
His gameplay is different to what we have in similar positions, whilst he is also quite a versatile player that is potentially capable playing deeper as a CDM in a double pivot as well as CM or CAM.
It's why this CDM is looking important to him. Say it was a more traditional ball winning midfielder like Rice; then we can have -
Bruno
Rice - VDB
Pogba/Bruno - VDB
Rice
Or the diamond type formation we see:
VDB
Pogba - Bruno
Rice
Maybe I'm wrong but I wouldn't write him off just yet and wonder if our replacement for Matic would bring up more performances showing the shadow striker version of VDB or the simple tiki taka passer from deep. The answer is probably a bit of both considering how Ole has used him a bit like a super sub so far in his time here and not much else.