As I've said before in this thread: McTominay's biggest problem is we're forcing him to be a player he isn't really and doesn't understand how to be. When you force a player whose instincts oppose the role, you're going to get constant reminders of that with the errors he makes, be it positionally, instinctive awareness of where he is or is supposed to be and in what he attempts to do on the ball in precarious positions.
McTominay's an offensive player who we've tried to force into a box-to-box, or even worse, a defensive role because he's 'big, tall and insert generic physical attributes supposedly associated with those roles.'
Essentially, he gets set up to fail because it's not a surprise he falls short when any nuance and know-how is prequisite. That's not to say he's good enough to take up an offensive role, just that if you're going to force him into any last line of defence role in midfield, he's going to struggle. The only way this could have been avoided would have been with some proper and intensive coaching, and even then, that is no guarantee you're going to change a players mindset and makeup on the fundamental level.
When it's said he's 'nowhere near good enough', I often think it's not fair on him because he's a squaddie at best, and if we'd recruited correctly, him coming off the bench with his powerful running and shooting, he would perhaps be perceived differently than the defensive-minded CM starter who was never that in the first place who isn't good enough to be at the club in any capacity.
Once we moved away from him being the runner sweeper-upper behind Fred, dealing with fires way up the pitch, he was doomed to fail. If there's one thing he can do is ball chase aggressively in behind a primary runner. It doesn't require the intricacies of what top class two-way CM's do and takes the onus off him having to think as that's left for others to do in and around him.
We should never have been in a position where we were reliant on him sitting or being an anchor in the first place, and in that case, you reap what you sow.