Well my point is stages like FD aren't so polarizing. If you got dominated on Smashville and you pick FD you are not likely to dominate back. At most you'll probably do a bit better. It doesn't make THAT much of a difference to the point where it's the main factor you won. Stages like RC however do in fact have an impact like this.
And no MK wouldn't still be as dominant without such stages like RC and Brinstar. And I repeat myself: These stages obvious were still legal BEFORE the ban. And I'm asking why.
In a recent France tournament they even banned MK but only for CP stages. Why else would they do this?
FD is the ONLY stage in the game without platforms. That right there screams "polarizing as hell."
You're right, your performance on SV and FD won't be that different, because SV is also a fairly polarizing stage. You apparently don't understand that our starter list is HEAVILY ground-centric. It isn't balanced between aerial characters and ground based characters.
As for your France comment, as the current starter stages are ground based, and MK is an air based character, ofc he's going to do worse on the starter stages. However, the starter stages aren't what they should be so it's irrelevant.
Also, you don't get to ask why something IS legal. Burden of proof is on you, you have to show why it should be banned.
*hint* If your reasoning includes anything resembling "they're gay" and "Metaknight..." your reasoning is bad.
RC is a moving, set-in-stone pattern stage that favors aerial characters. There is no randomness and there isn't any tactic on it that degenerates gameplay to focus entirely on it. Promoting "stalling" isn't a bad thing, it's just gay. Which isn't good reasoning. There is literally 0 reason RC should be banned (objectively). Brinstar is arguable.
Now back to the main point of it all, assume that every stage legal was possible to be a starting stage (known as flossing). Assume you have an aerial character (Wario) vs a ground character (Diddy). Almost all of the starter stages will be stricken (since they favor ground characters which is Diddy) and almost all of the heavy aerial based stages will stricken (since that is what Wario wants). Now, assume Wario wins game 1 and Diddy goes to FD. Do you REALLY think that there won't be a HUGE difference between the stage that is the median of bias and FD? If so, go to the stage forum more often and actually learn about the stages in the game. If not, than you agree that FD is just as polarizing as RC (because it is).