I hear you, but I think the time investment is as important as anything.
Buccaneers cut bait with Winston, won a Super Bowl not long after.
Eagles parted with Wentz, Super Bowl contenders not long after.
49ers cut bait with Lance, Super Bowl contenders not long after.
Rams cut bait with Goff, won a Super Bowl not long after.
Broncos cut bait with Tebow, won a Super Bowl not long after.
Every situation is unique, but what really kills teams is when they keep waiting for a QB who just doesn't have it to turn into something he isn't - especially when it comes time for that second contract.
I'd rather have absolutely nothing (which means having the hope of getting something in a future draft) than be committed to Prescott, Jones, Carr, and plenty other QBs in this league.