I’m not “cocksure that he can’t”, only sure that he has not and that he has a pretty large sample size to this point.
I was fully on board a year ago with trading the top pick because of Fields. He had shown some improvement at the end of the season and I thought he was likely to have a breakout year where he showed quicker decisions, more accurate and consistent passing. But that didn’t happen. He’s not really notably better as a passer than he was a year ago.
He has not been very good this year, and they have the top pick again. It would be a very obvious and easily avoided Bearsy mistake to pass on a QB again in the hope that Fields suddenly gets way better in a new system in year 4 with $100m+ on the line. Could it happen? Sure. Is it likely to happen? Not at all.