There's something to be said about longevity. Joe Burrow is the purest passer in the NFL by a large margin, but he's way more frail than Allen and Mahomes. The former run the ball a lot and can withstand punishing hits way more than Burrow. Doesn't matter how godly your arm is if you can't stay healthy to use it. Lamar was also in the Burrow category for a while, but has done a much better job in recent years at avoiding hits.