And Kaepernick also had the benefit of being in an offense that was on the forefront of the RPO revolution taking the league by storm, having one of the best offensive designers in the game, and excellent overall infrastructure on both offense and defense.
As I said, earlier, you have to take into account the context and extenuating circumstances.
You can put whatever context on it you want.
Prescott was not good in 2017 or the first half of 2018. His on field performance, for whatever reason, system or otherwise, more closely mirrored 2002-03 Quincy Carter and 2012-14 Colin Kaepernick in nearly all stats, than it did above-average quality NFL starters of 2017-18. That doesn't mean I would have traded 24 year old Prescott for 30 year old Andy Dalton or 28 year old Tyrod Taylor, because Prescott was younger and had potential, but the fact remains that is the tier he was in.... with busts and journeymen.... at that time.
If his performance of 2017-18 had continued, he would not be in Dallas right now. He was not good. His contract would have expired and he'd be gone.
The point to acknowledge here is that it wasn't some blip. He put together a run of poor games that outnumbered substantially his quality performances of 2016 (which also were not exactly great; more efficient and bus-drivery though, but he was not winning those 2016 games on his arm either, nonetheless). By game 7 of 2018, the only reasonable interpretation of Prescott was, a fourth round pick who enjoyed a magical rookie year supported by a solid defense and excellent OL/running game, who came crashing down to earth once teams got footage on him, and he was forced to carry more of the load himself rather than his supporting cast, and that he was not going to last.
A lot of QBs who hit that tailspin, especially slightly undertalented mid round picks, would never recover from that. They'd burn out and be done.
Prescott figured enough out, perhaps helped by a timely comfort move to add Amari Cooper, that he was able to develop after 2.5 years in the league into more than what he was prior.
It's a huge success story and we are the beneficiaries such that at least now we don't have to be pressing to find a QB replacement. Granted, we now have another dilemma - I think he's a top 10 QB but not a top 3 QB, but he wants to be paid like the latter. That's another big problem.