High QBR does not separate the QB impact from the rest of the team, the culture, player development, etc. Having good players to distribute the ball to, a good oline to protect him, a good scheme to operate in, good play calling, and a good culture of winning and growth are all going to positively impact QBR.
The QB is the most important position in sports. He has the highest impact on wins and losses for sure. But it is also true that he can't do it alone. I'm not sure there is a great way to separate those impacts since they all play together, especially the coach and culture.
But for the players, you could look at pro bowl and all pro players that they play with. That might be a way to show which QBs have to overcome more of a talent gap from the rest of the team and which benefit from dominant players at other positions. It still isn't great, but it is a start.