I'm probably simply overreacting to the Vikings game, where even a mediocre or regular-bad game is an easy Bears win. I don't know that "mojo" can go away and never come back, I don't think thats true. But there are mental skills that great QBs have that isn't reducible to simply intelligence - we know Fields is a smart guy and can metabolize the offense in isolation. The truth is, at this point, 2 and a half years in the league, he cannot execute that consistently on the field at game speed, which someone like Mahomes can do effortlessly.
The thing thats annoying is, and I must stress I am not saying Bagent has the makings of a starter or anything, but that he, (for one game that was actually pretty mediocre by the standards of the modern NFL) had that mental processing and quick-twitch responsiveness that we've longed for Fields to display. Even during his great games, its because he excels with his feet and in that intermediate and long distance passing when he's got time to throw.
Oh well. I just have to go through the phases of mourning with Fields, I guess.