I guess my experience has been that even casual players can get burned out on 5E, and a lot of the complexity of PF2 is more in theory. One great example is the three action rule. In 5E you can attack, move, and then attack again, which my difficult player had a ton of problems with for some reason. He'd always want to turn that into a double move. With PF2 it was "move, attack, move ... and you're done." Yes, the 5E rule of moving might have seemed more friendly, but it didn't work out for this player in practice.
I don't know if the complexity of PF2 will be a barrier after people rage quit, but I do think that exploring other games (any of them!) leads to better gaming for everyone. It also will hopefully lead to less "my group wants to play 5E, ugh!" threads.