Idk man, it's hard to explain my view on MUs I guess, but here's an example.
I think it's ridiculous how it's becoming popular opinion that the Marth - Mario MU is even or in Marth's favor.
The Marth player has to perform at a much higher level than the Mario player does. Mario is just copy-pasting what he always does.
Mario gets one grab and that is guaranteed 0 to 50 or 80 damage, maybe more. If he's been camping fireballs, that's probably another 15% or so on Marth. After that, he only needs about one Usmash to take the stock.
That means Mario only has to "win" neutral like twice each stock.
Marth has to get the right read on Mario's approach, without missing once. And each time Marth hits, his goal is to keep Mario out, and if he deviates from that strategy, he exposes himself.
Leo does this consistently because Leo is one of the 3 best players in the world.
Mr E and Pug both drowned in pools at ZeRo saga and Genesis 4. If MkLeo was not a Smash4 player, everyone's tier list would never have hyped up Marth.
Marth can beat any character, but so can Peach, WFT, Lucario, Palutena, DK, Bowser, ect... Imo, some of those characters are easier to use and win with consistently.
Like Mr E just played a local where he was sent to losers by some Corrin player, where Mr E barely had a small lead on the last stock of an even set, and Mr E went off stage to edge guard, and then he died after getting hit once, because that's what happens a lot when Marth goes off stage.
https://www.youtube.com/watch?v=XEVmPyukRwY
Then he lost to John Numbers again, as he has many consecutive times now, because Marth gets camped out by any character that can camp - which is most characters.
https://www.youtube.com/watch?v=W3c8ottKwvI
I feel like Mr R has lost to Leo's Marth so much because Mr R literally never tries to camp Marth out. But the two sets that Void's Sheik has beaten Leo, Void camped Leo out.
That used to be standard procedure in the Sheik Marth MU, then people just forgot how to play the game except Void.
Marth has an even MU with basically every character in the game imo, and loses to some of the "lower tier" characters, like duck hunt or Pac Man.
Mr E - one of the top ranked players using a top ranked character - lost to some random Pac Man a few times lately, pretty badly. And Pugwest got beat pretty bad by Raffti, a non top ranked Rob player. And the times Pug does win vs Raffti, it's always even.
I think Marth is top tier - if played absolutely perfectly. (But then, maybe that could be said about any character) Like, if you ever play a very good Greninja player... good freaking luck winning with Marth.
It's more difficult to play consistently with Marth than it is Mario or Diddy.
Diddy is in control of neutral most of the time, has an easier neutral, and a safer neutral - so imo he has the advantage. Diddy definitely wins the Marth MU, imo.
Sorry for writing a book, but I'm just saying - if Leo liked using Ike more, then Ike would probably be top tier right now.
Edit .
Case in point, a Vinnie style Sheik campy playstyle takes a big crap on Marth. Marth has to work so much harder than Sheik does. Its not 50/50.
https://m.youtube.com/watch?v=_jewPMNKSBA