Except that this kind of issue (i.e., samefagging with the most powerful mons) is exactly why Smogon exists. Too many people blame Smogon for forcing them to drop some of their favourites because they are not fit for OU format, but this is forgetting that:

1) There are other tiers documented by Smogon like UU, RU where your fav might fit well.

2) When a single mon forces half players to modify their teams to not be stuck of fucked in advance when they encounter it, the game is not balanced. Just look at MegaMence: sure it is cool (actually one of my favourite mega), but it is way too powerful: 120 base speed, a surprisingly high defense (130) which is further reinforced by Intimidate the turn it mega-evolves (forcing most physical sweepers to switch out) and a 95 base HP make it a flying tank powered by rocket fuel. And you can barely point out it has a relatively low Attack for a Mega (145 is not exceptional; mega Tyranitar has 165 for comparison), as Aeraliate makes Return a 200 base power Flying-type move. It has very few counters in OU, so having a guardrail like Smogon prevents such threats from polarizing the metagame and makes it healthy. The same went with Garchomp in DPP games, if this example speaks better.

Plus, the tournament here is organized by Nintendo (and not Smogon), which does not really care about all that and even allows players to pick Uber-tier mons from time to time (with a limit, like one in 1v1 and 2 in 2v2, I think).