Who would trade anything of value for Fields? He was easily the worst starting QB in the league by DVOA and DYAR (34th out of 34 qualifying QBs in both) this season. By ANY/A, he was 33rd out of 33. By passer rating, he was 25th out of 33. By QBR, he was 17th out of 33, probably because of all his rushing yards. And of course, between all the rushing he did and the enormous number of sacks he took (sacked on 14.3% of all dropbacks, miles ahead of the second-most-frequently sacked QB in the league, Russell Wilson at 10.2%, with no other QB above 9.7%), he'll have a lot more wear and tear on him than most QBs with two seasons of NFL experience have. Also, he fumbled a lot, leading all QBs in the league with eight fumbles.
Now that Fields has had two seasons among the worst QBs in the NFL, it looks to me like the "decent NFL starter" ship may have already sailed for him, so is there any good reason to believe Fields has a better chance to be an adequate NFL backup than any "project"-type draft prospect or journeyman career backup? And how much would a team trade for that?
Since Fields was drafted in the first round, his salary and bonuses are fully guaranteed for two more seasons. Yikes. So even if the Bears wanted to cut bait and draft a QB they believe might have a better chance at decent performance in the NFL, they'd have dead cap if they traded Fields. There'd be some cap savings for 2024 despite the dead money if they managed to find a team willing to trade for him after the 2023 season, but if they trade him before the 2023 season, they actually end up losing cap space.