I don't really know what you're expecting out of a young QB at this point. Even if the Steelers somehow had the #1 overall pick, anyone QB they take is likely either going to be raw with huge upside or safer with lower upside. The idea of getting a QB with superbowl caliber upside but without any sort of risks or flaws with his game is simply not a thing that happens much. Even Mahomes had some major question marks going into his draft year.
There have been 15 QBs taken in the top-3 in a draft in the past 10 drafts (2014-2023) and I'd say that only 3 of them (Stroud, Burrow and Lawrence) had that "high upside without major risks" label on them. And even then, Lawrence really hasn't panned out on that upside either.
I accept its always going to be risk vs upside.
I do not believe Fields type athleticism has any particular correlation to a QB's upside.
I do believe that a high pressure to sack ratio is an unacceptable risk barring some weird tic to their game. Of all the NFL QBs drafted since they started measuring this, Burrow is the only guy to have a high pressure to sack ratio through college and become a star. Burrow is a freak. If we'd known now what we know now about pressure to sack, he'd have been regarded as high risk. Mayfield is the next best QB with that stat. Everyone else is a bust (barring an unlikely career resurgence from Fields). That makes sense to me as the most likely reason for a QB to accrue this stat - and it is very sticky from NCAA to NFL - is they simply don't realise they're in trouble quick enough because they don't read the game quick enough, and that's a killer. Guys like Burrow who do read the game quick enough to get the right pass regularly, but take big risks to get the right pass and who don't have the athleticism to escape sacks are rare. I suspect how often he gets sacked also might have something to do with the constant injuries too.
For me, for upside, I am looking first and foremost for things that indicate they have a high football processing speed and are big moment players. To me, those are the two biggest indicators of upside. Arm talent comes next. Like athleticism if it's there, but I'm mainly looking for the strength and agility to escape sacks. JJ McCarthy had nowhere near enough passing responsibilities in college to feel safe about him not to mention he just fires it without touch a lot, but I think he showed enough big time moments and ability to handle pure passing downs that I was interested. Strong arm too. I think Bo Nix's stats and tape suggest he might have that processing too, although I'd be a bit more nervous there given his long college history. Anthony Richardson should have gone back to the NCAA and learn to pass, but the reports that he aced his S2 test and his very low pressure to sack ratio makes me intrigued in the idea he could be the next Josh Allen. All three guys have big risks, but I can see upside.
I look at Jalen Milroe and I don't see upside and I see unacceptably large risks.
edit: p.s.
a) Yeah, it might be harder to get a safer prospect than Milroe who has genuine upside at 20ish but that's why I'm all for bundling up those picks and moving up.
b) If we're looking for raw QBs with upside traits, I'm currently looking at Weigman and Allar. Young guys with raw mechanics but who display some high processing traits and numbers. Bad week to say it about Weigman! But see how the season goes. Bonus marks for Allar in terms of, if I'm looking for an athlete at QB, then the 6'5" 240+ guy who can see over the pocket and ragdoll smaller defenders is my guy.