I agree, but he explained why in an interview last week, I think - Conte basically tells him exactly what to do, when to do it, whom to pass to, and where to position himself.
You can't really fit Sanchez into a system where he has to make instinctive decisions, I suspect - because he usually gets them horribly wrong. Overcommits, positions himself badly, makes the wrong call too many times.
Mourinho's system was basically this - he relied on players to make decisions on the field, and Sanchez struggled terribly.
He does well in two types of systems - Conte's type of relentless drill where the instinctual decision-making is taken out of his hands, and pressing systems where he can use his pace to play the role of the last man in the back line pretty well.
All that to say, I think he's done well and Romero won't walk back in when he comes back from injury (and nor should he). Right now, that RCB slot is Sanchez's spot to lose.
But do I think he's improved the long-term deficiencies in his game? I'm unsure. I think a lot of players look better than they are right now because Conte's system brings the best out of limited players ,and I think Davinson benefits from this.
But not every coach is as thorough as Conte. And down the line, *if* he stays, we'll need him to make decisions and take control on the field again at some point. Can Sanchez do that? Jury's out, imo.