He's got more disjoints than
all of the good characters--sometimes
combined--with the exception of Luma (which only partially counts because it takes damage in some way when getting hit) and enough mobility to keep opponents out of close quarters, which enables him to abuse that disjoint.
With just an in-place SH airdodge, Marth covers a huge radius of space between up-air, f-air, and b-air that can punish almost any commitment. Heck, the simple act of Marth
moving away from you spacing puts the ball in his court because if both players delay a button press for as long as possible Marth's going to win out because of his massive disjoint. Just watch the first game of Leo vs. ZeRo and you'll see how difficult it is for Diddy to get into d-tilt spacing range because Marth perfect pivoting backwards is so scary (the threat of jab is huge, and at death percents, any tipper tilt or aerial could be death). It's not even just that one yomi exchange, though. For
every option that Diddy has in neutral, from holding a banana and waiting to f-air walling to dashgrabs to d-tilt spacing, Leo had a lot of counterplay available to him, from short hop reaction f-air to dancing blade to pivot f-tilt to perfect pivot jab and more. It's incredible to be able to contend with a character like Diddy Kong in the neutral and have
multiple options for doing so.
But it's not just about winning exchanges or creating counterplay/set-play moments, because reacting in this game is precarious enough to force guesswork at least some of the time. Sometimes, Marth just hits you on a guess, like an anticipated shield drop for a delayed f-tilt, and with good spacing such a guess will threaten
kill you at virtually no risk to himself. It's not the same as Mario reading a roll and f-smashing, because these moves are Marth's
long-ranged,
disjointed tilts and aerials. Marth's "hard reads" are hardly reads, because they often don't lead to punishment.
Literally all of his relevant moves (except the poking move d-tilt) have this quality at reasonable percents. We're not talking about an advantage-state conversion. We're talking about a straight-out-of-neutral-you-just-slammed-into-the-blastzone-son one way trip to death. You get hit by one guess in the middle of the match and you just explode.
Tipper is not an advantage-state mechanic, it is a neutral mechanic; tipper forces you to play in a certain way to avoid getting obliterated by a random hitbox.
Finally, jab has one of the best (hitbox*reward) : speed ratios in the entire game, it's totally bonkers how much stuff jab leads into with that big of a radius, and it's applicable to a wide variety of situations in neutral. In fact, for many characters, "ideal play" against Marth involves getting close enough to suffocate him in close quarters, which in turn means setting themselves up to get jabbed. Which is beyond hilarious.
Character's neutral is mad good.