If he hides from the ball and its an issue, why cant the coach just teach him where to be, so he will be in, most of the time, a safe spot to receive a pass and he just have to pass it elsewhere? Or back to the teammate that passed to him?
For a professional footballer I doubt that aspect cannot be taught. Its a simple pass and move. He is not great at controlling the ball but not terrible or awkward and slow like Fellaini.
As I said I can see him as a squad player and I think he will be alright with such a role. We shouldnt expect him to play a hollywood ball or to beat players. We just need him when our main midfielder needs to rest and we need a pair of fresh legs. He can be the Darron Gibson of Fergie days.
He has always, throughout his entire career, got on the ball significantly less than all our other main midfielders. It didn't matter which position he was playing, whether it was as a 6 or an 8, his poor movement meant he simply received the ball less than other players when they played in the same position. Instead of moving into space, he has a very bad habit of moving around keeping an opposition player between him and the ball so that he isn't a passing option.
I always remember the time a few years ago that we passed the ball from Shaw on the left, through to Maguire, to Lindelof and finally to AWB on the right, each of them looking to pass it forward, and McTominay slowly jogged across the width of the field keeping an opposition player between him and the ball the entire time. It wasn't until the ball went to AWB that that player actively moved in a different direction and Scott found himself in a bit of space...only for him to quickly jog over behind a different opposition player instead so he still wasn't an option to pass to. If I didn't already shave my head I would have pulled my hair out that night. I think it was earlier this season that somebody on twitter uploaded another similar situation, but it's the kind of thing he does regularly.
Is Scott doing it deliberately because he doesn't trust himself to receive the ball? Is he doing it accidently because he just doesn't recognise where he should be moving to? Are our other players actively trying to avoid him because they don't trust him to receive the ball? Nobody knows for sure. Probably a bit of all of them. But the end result is the same - we've got a player in the heart of our team, the area of the pitch that is normally used to control the team around, who not only isn't capable of doing much when he gets on the ball, but he regularly makes it easier for the opposition to shut down our play by not providing himself as a passing option.
ETH has come in and actually seems to have done the opposite of what you said. Rather than train him to move into better positions to receive the ball, he seems to have decided that he wants Scott to get on the ball as little as possible. Throughout his career he's generally got on the ball about 20% less than our other midfielders (with some games where it was much worse), but last season under ETH his possession stats dropped even further and he he received the ball almost 40% less than the other player used in the same position (Casemiro). If that is the case and ETH's way of getting around Scott's lack of ability on the ball is to try to actively avoid him, that is obviously a very big problem in it's own right.
This season is a bit harder to judge, as his touches have dropped even further but Mount and Mainoo tend to also be almost as low when used in that position as well. So it could be an aspect of the system that that player does get on the ball significantly less than the other two midfielders, or it may just be that Mount didn't really get going and that Mainoo is an 18yo breaking into the team, so it's more understandable that they aren't quite up to speed yet compared to Scott who doesn't have those excuses.
