MavenMy main point however is that the reason sniper is so hard to kill us because he has a team protecting him at all times. He is clearly weak to stuff or else people wouldn't need to sit on him.
This is a flawed argument. You don't sit on the sniper because the sniper "needs it", i.e. they would be useless or bad otherwise. You sit on the sniper because it is worth it; sniper is so good that it is entirely worth dedicating classes to just sit on them and afk to support. It's a very deliberate choice that people make; the value add of an engineer actually playing the game is seen as lower than just placing them in a no man's land like lakeside ruins or back of product cliff to lower the odds of the sniper getting stabbed.
Of course this alone is not evidence that sniper is broken (could be the case that engineer/pyro are just that bad, though I sort of doubt it), but the argument that people sitting on him = people need to sit on him is quite poor. Empirical evidence shows you what is perceived as being optimal, and optimal is not the same thing as necessary.
MavenIf teamwork is actively being used in the argument for him being too powerful, I don't get why it's ridiculous to say that teamwork can be used against him.
Not all teamwork is created equal, to just treat them as the same is at best seriously misinformed. It does not take that many brain cells to play pyro and just sit on your sniper; it is much more difficult to coordinate pressure on the sniper (especially if you currently don't have one) so you don't just die during a dry push.