Your entitled to your opinions but it's based on a hypothesis, so it can't be proven. I think with better play calling and a better roster, he could have been a top 10-15 QB. ( His last 7 games he was the 11th ranked QB) The lack of trade value has a lot to do with timing. Poles didn't decide to trade him until well after the combine, after most spots were filled.
There are 2 reasons he's not here. We got lucky and got the top pick, if we didn't have a top 3 pick, he would still be here. Also having to pay him big money in 2025 and forward came in to play. He hasn't shown enough to get a big contract.
I think he proves himself and becomes a starter in Pittsburgh. He's never going to be elite but obviously history tells us you don't have to be to win a SB. Poles choose Caleb because he can become elite and that doesn't automatically mean Justin is a garbage QB.
All of this is my opinion and can't be proven until a few years have passed to see if it was accurate.