Why class limits are important:

Triathlons are made of 3 sports everyone competes in: Swimming, biking and running. A competitor has to be a good in all 3 to get first place. If a Olympic-level runner saw that sport, they would vote to ban swimming. They can vote to do that of course: Make swimming shorter, make it count for less. That would give competitive advantage to the Olympic runners, and they would enjoy that a lot.

Good runners would naturally want to win by removing the other 2, and running is more popular than swimming, so they could easily vote swimming away from triathlons. But triathlon without the 3 sports is no longer a triathlon

What I am trying to say, is that 6v6's current rules, through votes of the majority, haven't been constructed with TF2 in mind, they have been created with Scout and Soldier in mind. And being good at anything else is - despite being core part of TF2 - not fun for the people who are exceptionally good Scouts and Soldiers. And while I understand the sentiment that fun comes first, that goes both ways: Why would non-Scout players and non-Soldier players find it fun to play a format that focuses so much on those classes?

I understand completely, learning new skills and adapting to a changing landscape might not always be fun. But that is the heart of competition, and that's where fun should be derived in a competitive setting. Any "fun" that is derived from no need to learn, adapt or improve isn't competitive.

6v6 is not a natural competitive development

My harping on Scout and Soldier might seem arbitrary and unfair. That is fine. Let's discuss objectively the consequences the class limit rules and how they affect game.

In Highlander, every class has restriction of 1. With 9 players, this forces 1 of each class. However, highlander never seems to devolve into a stalemate where neither team is attacking or defending. The "flow" of a match is pretty similar to a casual match in this regard; Both teams slowly poke at each other, then explosive high-value picks (Heavy, Demo, Medic) ensue, the winning team pushes the advantage and the teamfight is quickly over. (Of course it is more nuanced than this)

However, the consensus in 6v6 seems to be that allowing heavies or pyros to even be viable (which is the sole reason given for Fists of Steel, Detonator, and Scorch Shot bans), will eventually lead to a slow, boring meta.

But that makes no sense. Highlander seems fine with these weapons. Sniper can easily kill Heavies, and Pyros lose against all hitscan weapons. So why can't a team break through a stalemate by switching classes to, for example, Sniper? (who counters both Pyro and Heavy) Most issues with stalemates seem to be caused by 5CP's brittle balance, but if that was the sole reason, people would've banned 5CP. So these balance issues seem to go deeper, affecting even KOTH and stopwatch.

And then it hit me. The class limits in 6v6 are weirdly specific. There can be 2 Scouts, but not 2 Medics.

Think of it this way: Would it be healthy for the game if we could stack Medics? Of course not, more players would be forced into over-centralized, Medic-focused meta. Everyone should agree that stacking a class creates issues, mainly of over-centralization.

And over-centralization eats away at the competitiveness of needing to adapt and learn. A player can't take the risk of running specialist class that has narrow use cases, because at any moment, 5 out of the 6 of the enemy team's players are probably playing as wide use case, generalist classes. And those enemies can't risk to swap to specialists either for the same reason. This type of circular logic is what creates overcentralization.

It doesn't matter if a player would find it fun to play other classes, or if they would be better with other classes. The meta is so overcentralized that nobody can pick specialists. (except rarely in lasts of 5CP)

Class limit of 1

If players were FORCED to pick specialists via a class limit of 1, this problem should be solved. I am not saying it will be more fun for the Scout players, but it would bring more competitiveness to the game. The ruling doesn't need to arbitrarily pick between Medic and Scout overcentralization, all classes can be affected equally. And if this change leads to another static meta, we can proudly say that the meta was natural.