This whole thread ignores the fact that we have nobody else (until Gomes comes through) that can do what Pereira does: play #10 in a high-pressing system. Mata is too slow, Pogba doesn't have the work-rate and Lingard doesn't have the delivery.
People who want Fred and McTominay to play 4:3:3 in a double pivot with Pogba ahead are saying that they don't believe in the high-press system that Ole clearly wants to play - Pogba can not press with that intensity. They may be right, and it may be correct that Pereira isn't good enough, but after literally one game in the new system we don't have the information to know for sure. And if you want us to play 4:3:3 that's okay, but it's not what the whole team has been practicing through pre-season.
Personally I think Andreas did okay: he worked his ass off, got two tackles in in the first five minutes, attracted the foul that disrupted Chelsea before the penalty incident and assisted a goal. Did people go past him too easily? Sure. But our whole midfield was porous. And a lot of the reason people accuse him of "being positionally unaware" is that his job in Ole's system is to support the high press, which means that if the press is broken, he is the mid-fielder who looks stranded. That's not his fault when the press is going around mid-field via the gap left by Rashford.
Lingard and Fred are not direct replacements (well, Lingard can be, but with less creativity). Gomes might be the answer, but not for the majority of the season. Andreas is the best #10 we've got for now.