He is normally 5th choice CM in a 4-3-3 for two interior positions after Pedri, Gavi, Kessie, and De Jong. Xavi probably was not thinking we were going to play the 4 midfielders at once as our first-choice tactic this season.
He should not have been put into this position to play as the most advanced midfielder and an attacking third player in a decisive season-defining game, but the change of the system, injuries and suspensions have done it. I like him at CDM more anyway. You cannot expect Roberto to start playing like an offensive midfielder after seasons of being a workhorse (before he started getting injured) and fullback.