Ik this is hella late, but yes, pyro is the easiest class to master since its mainly just holding w+m1 and the occassional m2, but soldier is the most recommended class as its versatile and well rounded for all situations.
I don't think what he said is right, because, even though it could be played like that, the class isn't just that if you start going out of the comfort zone
The biggest example is the combo pyro and another one is the fearsome one: focusing on causing panic on the enemy team, making easier for your team push. Also the support Pyro (Pybro) that deals with spys and helps engineers and even heavys (trust me, support heavies when they are making a push)