If Mario really, truly lost to every top tier and just had "average traits" I don't think two different players would have won incredibly stacked majors with mostly solo Mario. I don't even understand where you're getting this conclusion that he loses to "pretty much every top tier", anyways.
Claiming Mario has solid stats all-around is completely false. He has some of the best moves in the game (bair, uair, nair, dair, usmash/fsmash, dthrow, up-b) alongside notably not-"average character" traits such as top tier boxing, juggling, air game, and damage/kill potential.
Blade Beam is really bad and has just worse overall data/usability than Fireball. Cloud's onstage presence is hindered by his weak grounded game (poor throws+terrible grab, lack of a safe grounded poke, etc. His best move on the ground is just super camping.), something that Mario doesn't have to worry about as much (mostly due to his amazing grab game and strong grounded normals).
If Cloud really, truly were just straight up better than Mario he would be filling top 32s (he doesn't) and Cloud players would have won majors already (aNTi's pocket doesn't count).
Cloud's disadvantage is also a notable flaw that continues to rear its head. As Cloud counterplay continues to evolve, so does the edgeguarding. While Down Air is a silly, silly move, it isn't invincible and people are aware of this. Cloud is combo food and his weak recovery is continually exploited.
Cloud nerfs hurt a lot more than people realize; the roll weakening was somewhat notable, and the LCS nerf was a slap on the wrist, but the Up Air change was huge. Cloud lost a safe poke and a reliable killing juggle tool.
This is pure theory and doesn't reflect upon the rest of your post at all.
Winning/losing a specific and somewhat uncommon matchup (which he doesn't actually "get shut down so hard", you're gonna have to explain that) doesn't make a character better outright. That's not how tier lists work.
Mario, from a purely statistical standpoint, was already everywhere in tournaments at every skill level. Just because he isn't winning tournaments or carrying players or whatever doesn't mean he isn't top tier.
I don't understand how "no one can just win with Mario" proves anything. What is that supposed to mean? No character can just cruise you to top 8 in this game's current state.
I said he lost to them, not lost incredibly hard. Like I said, Mario's disadvantages are never huge, nor are his advantages. It's still perfectly feasible to make it through a tournament of top tiers with him, you just have to be really skilled (like Ally, or will we pretend Ally isn't really skilled?). That still doesn't change the fact that every single one of the top tiers does have that slight edge against him.
I'm aware Mario has some particularly good moves, but I highly disagree that he has THAT many "best moves in the game", especially when some of them are explicitly outclassed by similar moves, like Captain Falcon in the U-air department. Like you're literally the first person I've seen say that and I can't see how you can reasonably argue every one of those is that good, not that you even attempted to here. Mario's my third best character too and so I sometimes stop by places where Mario players congregate, and I have not seen anyone say this.
Blade Beam can completely cancel out Mario's Fireballs due to the size of them (and the two moves are about the same in cooldown), as can Cloud's sword swings. Cloud's grounded normals aren't much of an issue when he has short hop N-air and B-air. In other MUs, Cloud's Blade Beam may not have as much utility, but Cloud has other things going for him in a lot of MUs, more so than Mario does. And when he has the advantage against Mario, even if not by much, I don't see how you can argue he's better than Cloud. Also, I never said his traits were "average", I said "solid". Big difference. Telling me he has "notably not average" traits is literally telling me what I already said myself.
Cloud hasn't been in the game since launch (let alone since the franchise started), so it's understandable he hasn't quite settled in yet. He's still progressed way faster than Mario did, though, which speaks volumes.
Rosalina wins the Ryu MU pretty hard for a few very simple reasons:
-Rosalina literally has the best aerial acceleration in the game (tied with Peach and Palutena), Ryu is among the worst in this department (an intentional design choice to replicate how jumping in Street Fighter feels - he essentially can't turn around mid-jump in a timely manner, most of the time you won't get a chance to). This means when Ryu makes an aerial attack, all of which have long lasting animations, he is COMPLETELY committing to it. On the other hand, even ignoring the extra defense and spacing advantages of Luma, as well as stuff like RAR Luma B-air and Lunar Landing, Rosalina does not have to commit to aerials nearly as hard, as she can easily swivel in and out. Rosalina dominates Ryu in the air, and in the short hop game.
-Ryu has trouble dealing with characters that can zone him out. Rosalina is one of the best at this in general. Ryu's own projectile is way too slow to be much of a threat to a character who already doesn't have to worry about projectiles nearly as much as anyone else in the game due to having both a meat shield and a move that sucks them up and temporarily makes projectiles hers until they disappear.
-Ryu has a poor recovery, and it's especially exploitable by Rosalina. And once again, he has to commit to every action he makes in the air. Rosalina can at least afford to stall and can just quickly launch to where she needs to be, even if she has no hitbox on her recovery. Rosalina is also especially good at gimping characters, and again, Ryu is easily gimped.
-Rosalina is actually notably faster than Ryu on the ground and in the air so Ryu absolutely cannot be aggressive against her. At least characters like Captain Falcon and Sonic have some grounds to attempt this, especially when they get rid of Luma. Even when Luma is gone though, Ryu is pretty non-threatening to Rosalina because he's slower than her anyway. As much as I don't do this personally, Rosalina absolutely can just stall and wait it out if Luma is KO'd against Ryu, because she's faster than him all around.
-Ryu is an insanely easy juggle target for Rosalina & Luma's U-airs due to his weight. Don't need to say more on that, their U-airs are infamous in general.
-Focus Attack is not very useful because when Luma is in play for surprise counters or even for getting out of U-air juggles, because Luma will immediately follow-up every attack Rosalina (sometimes it's actually the other way around, depends on the move) makes and Focus Attack only resists one move at a time.
Rosalina and Ryu are generally regarded as two of the best right now, but regardless of whether or not you think they are higher than other characters, Rosalina is above Ryu because the match-up spread is either even or in Rosalina's favour, and at that point, you have to look at the match-up both characters have against each other. And Rosalina just has so many notable advantages against Ryu to the point Ryu doesn't even get to make use of many of his main strengths. He can't even combo Rosalina that well because she's light and floaty and she often escapes and counters back, even if Luma isn't there to do it.
Nice
