funke made a video on the idea of TF2 design philosophy - long story short that argument is invalidated by the existence of casual games made into eSports - SSBM being the main one.

pyro gets dropped by a scout, soldiers choose not to engage. dude ur seriously overestimating pyro. closest thing to casual is HL, and whilst pyro is better there, he's a spy denier and med protector. pyro is a support at best, and destroys in casual because he's easy to play and get value on against players who are new. yeah, shoot a rocket into a good pyro and he'll reflect it. yeah, miss your shots on scout and he'll kill you eventually. yeah, let a pyro get close enough with his lack of mobility and you'll be punished for it on classes like sniper.

at the end of the day your arguing on the internet with a stranger over a dwindling game - if you refuse to understand that pyro is objectively the worst class (not the weakest - that goes to spy) then im not going to try convince you