Agree with most of the rest of your post, but not this, other than he isn't "world class", not even close for me.
Sterling is 10 inches shorter than most of Burnelys back 4, so keep crossing the ball was a fault of other players for me, he was totally isolated for the bulk of the game, I didn't think he did a lot wrong, until he went wide, when he just didn't do enough at all. It must be quite frustrating to be the CF against the biggest defence in the league at his size, and the ball keeps coming in at their head height, that's poor play from others for me. Foden went there for a period of the second half, and got the same shit service.
I think for his own benefit he probably needs to move on, though I'd first tell him to play back on the right, where he has been very good in the past, and run at the full back, because right now on the left he stops the play, and in the middle he looks clueless.
A player seriously out of confidence.