I think the problem Ole has is the system is flawed due to the players we have. Having thought about why we don't have a functioning style of play.
If you look at Chelsea, City, Liverpool they all know what the roles are. Even when players are rotated, the players coming in know their roles.
With United no one knows because one week we are starting James on the wing who is a winger, then the next we have Greenwood who is a inside forward.
One week we have a LW who is a winger, the next we have Pogba who is a midfielder, so the team shape is different on a weekly basis.
It makes it hard to train patterns of play because you have to account for so many different variations of play.
I think, that is an interesting take on it. Depending on your own stance though, it can appear as the chicken-egg-situation, wouldn't you agree? Because there are no absolute dependencies, it is a complex issue.
The team shape, formation and game plan for a specific match are not locked on the players you have as a law of nature. It makes sense, to choose a shape, formation and game plan that emphasizes your players strengths or your opponents weaknesses but the manager isn't forced to do it. Also there isn't one right way for a manager to make his decisions: do I create a plan based on the best available players to me or do I create a plan and choose the best fitting players for it? The question is also answered differently if you look at it on the base of a "one-game"-timeframe or over a full season, potentially even longer.
I don't know, if I understand you correctly, but I think, using the set of available players as a reason that we play the way we play is faulty for two reasons:
a) players follow instructions on how to play so James and Greenwood absolutely can do the same role theoretically (even if a certain task might suit one of them better or worse) and
b) Ole is (at least heavily) involved in recruitment so he should have identified the players needed to fill the roles he wants to play with and/or should be aware which roles cannot be filled with certain players (for example Greenwood will not give a lot of cover for his RB most of the time so having him there will ask for compensations potentially)
When roles are always defined newly based on the available personel, it can block the maximization of output long term (not just in football, this is also a big thing in start ups btw) which very well might be, what we are seeing with United these days, but what we, on a certain level encourage and want, when you look how many on here try to put for example Pogba and Rashford in the same lineup at all costs.
I would agree with the observation, the back and forth in personnel might have an decelerating effect on the natural development of patterns of play. But on the other side, these patterns of play could also be instilled in other ways than just on match days if such patterns would be identified and defined. That they are not (not obviously at least), indicates to me, that our management teams focusses on different aspects than this (admittedly to good success).
All in all I think, the players aren't the root cause for what we are seeing, it is that our coaching teams tries to maximize output of the team by giving them mostly freedom to express themselves (which is great if most players are on song) and I would also agree, that this is a bit reminiscent of the Fergie-days. That isn't a bad approach per se and the results of the last 2 seasons support that.
I think, where this approach falls short though, is that such an approach isn't the norm these days so while some players thrive in it (for example Bruno) other players may find it difficult to get going (for example VDB) because they are used to more rigid systems and fixed roles that can make it easier to bed-in new individuals. This would explain two things: why we sometimes do not look like a team that plays football together 12 times a week and why the drop off was as big during the last seasons as soon as "the fringe players" had to play only to be bailed out by 1st teams offensive players in many situations.