People who think that Pyro doesn't have to aim. Real Pyros know how to make all their flamethrower particles land by curving them and leading targets, for maximum damage.
Seriously, look up how the flamethrower's particles work, they're not easy to control. And boy, aiming airblasts isn't easy either, you have to account for the time it takes for the projectile to move close enough to airblast, and to travel to your target, and aim accordingly, making leading targets twice as hard.
The flaregun's crazy arc? Getting meatshots with the shotgun? Also not easy to do if you're not aiming.
some people are mad in the YT comments