Didn't I hear that most of Europe uses customs from someone in this thread? What about those players? Why alienate them to cater to the Japanese? And why should we care? In every game, we rarely, if ever, get any regular attendance from international players. I can think of Armada, Leffen, aMSa, and Abadango, and two of them play Melee (the more established and I believe more popular worldwide game). Unless we change our rules to mimic Japan's ruleset exactly, we aren't going to attract many players. And if you want to have that ruleset, you might as well just rank players by their For Glory winrates.
Theory crafting doesn't work for competitive Smash? Then why do we care about frame data? Why do we debate matchups? Why do we even have a tier list? Theory crafting does work, but it's up to us to test the theories that pop up. And don't say Evo counts, that's one tournament ever to use customs. Top level players don't use customs, so they don't know customs, so they need to work harder to beat people who know customs but aren't as good players. This is why they think customs are "stupid" or "jank", not because His Holiness ZeRo spent hundreds of hours in the lab, researching every matchup created just by changing a character's customs. What he did was see that customs are boring to unlock and all the butthurt scrubs who think Wind Dong is OP, then decide that customs are stupid, regardless of their potential.