Just to address some of your not good points from my own perspective, of course others will argue otherwise I'm sure
1&2 - Kinda the same point and I do believe we have played with a high press quite often throughout the season but for me I think lack of fitness has been a serious issue quite often. Our injury list and of course fitness was a huge, huge issue moving from the Jose tenure. We topped the injury list table for 17/18 and 18/19 I believe or at least 2nd behind Spurs.
To carry out a high press requires very, very high levels of stamina and avoiding injuries and the longer he is here the better our fitness is and injuries are decreasing.
There is one other area that fitness falls into then as well and that is squad depth. Logically speaking if the same 13/14 players are routinely playing fatigue becomes a serious issue and it is extremely difficult to be making substitutions when he is making such a dramatic decrease in player quality from a Pogba to Fred or Bruno to Lingard and that is currently the status quo.
3 - Basically touched on it above, when you lack real quality in your sub / squad options it isn't so much that the subs decisions are "garbage", more so the subs themselves are garbage as highlighted in the examples above.
Point 3 kind of reminds a year ago where so many Ole hating folks (not saying you), were adamant he saw Lingard & Jones as United level cause his hand was forced into playing them due to the aforementioned fitness / injury crisis he had at the back end of last season.
4 - At a guess I'd imagine there is little faith in De Gea currently and its making for a nervous back line but to add to that, Ole wants us to play out from the back and it is very difficult to do that when fatigue is setting in as we've seen in recent games.
I could go on with a long analysis but I'll let this extremely informative piece do it for me, it highlights the difficulties Ole faces when he does drop a Pogba / Matic to McTominay and also the tactical issues he faces in doing so in turn.
https://thebusbybabe.sbnation.com/2...5E2PdX4RzGOkXYDBNjQ-VXxt0DzcEPwyP7P3M8P_iQK1E