TynnyriI'll focus on the main part of your reply: You are defending the current arbitrarily constructed meta by pointing out that it has been constructed arbitrarily at all: Instead, it is intended to maximise skill expression.
the 6v6 meta was not decided on "arbitrarily,'" like i just said, this game is old as dirt, and 6v6 has been played for twice as long as overwatch the video game has existed. the format has been arrived upon by a consensus of the people who actually play the format, determining that the standard setup is what works best both for maximizing winning potential, fun for all players involved, and to maximize the pace of the game. nobody just threw darts at a board and decided how many of each class you get to have on one team.
TynnyriSo then, why would there be an exception for Medic? Medic is the most important class in the game, but far from the most skill expressive. Without medics, lot of stalemates would never even happen. After all, you are less punished from taking damage when you have a medic in your team. Wouldn't that be a source of negative skill expression? Medic makes the game easier, and patches your mistakes.
i actually agree that medic is devoid of a meaningful amount of skill expression that makes him fun enough to actually want to play. there's plenty of evidence of this, especially when you look at how few medic players there are on RGL pugs (though that has other contributing factors unrelated to the format lol)
the issue is that medic is a necessary evil. tf2's entire design, no matter what server you're playing in, is hinged around ubercharge. many a choke would be nigh impossible to push without it, and even in pubs, the medic is the most important class in the game. he enables you to be able to explosive jump and engage with the most fun part of tf2, its movement. he minimizes downtime to keep you engaged in actual combat, and he breaks stalemates when the other team doesn't have means of countering the uber (by way of their own or other things like explosive or airblast denying)
i think if you've played a decent enough amount of tf2, you can realize how disingenuous this argument about medic is. the game literally is built around him. i do certainly wish he was more fun and still expressive to play, but honestly surfing damage and hitting arrows is already more fun than fucking Pootis.
TynnyriYou also mentioned that Pyro has weaknesses that Soldier doesn't have, and therefore it makes no sense to switch to Pyro. And that's a perfect explanation for why 6v6 games tend to slow down: As you said, the current arbitrarily chosen meta (2 scouts, 2 soldiers) revolves around the fact that Soldier and Scout have very few weaknesses to exploit. (...).Your explanation of weaknesses gives an eloquent explanation to the source of stalemates, giving light to how stalemates might be solved: By weakening team compositions.
your solution to stalemates in 6v6 is to... make everyone play Worse classes that are Less fun...?