First of all, I don't think McTominay is a holding midfielder, nor should he play there. However, let's not go on like we weren't conceding those kind of chances with Mainoo on the pitch. Let's go back to Villa, for example, McGinn was free in the area and had it not been for Evans, they'd have gone 3-2 up.
As I said in another thread, the kind of goals we conceded yesterday, i.e from a cut back, are goals we've been conceding for a long time now, regardless of who is playing there. Its a structural problem! If people can't see that, then they're being ignorant.
If ten Hag wanted to lessen the amount of times this happens, then he needs to go with a double 6 pivot with a number 10. That way, if/when it breaks down in midfield, we have 2 holding midfielders screening the defence. City do it with Rodri and Kovacic, Villa with Luiz and Kamara, etc. Heck, Ole used to do it with Fred and McTominay. Whilst they weren't great in the creative department, we were a lot harder to beat, especially in the so called "tougher" games.
Unfortunately, if ten Hag continues to play the way he's playing, and purposely ignore how vulnerable we are to counters, then he'll lose his job. As a manager, he needs to identify this flaw and change it. Plus, we look much better in a 4231 anyway.