Why would Meowth in any way be similar to Meta Knight and why would it matter when Corrin is another visually interesting Marth.
I think comparing the cat and the bat is really reaching for the sake of reaching.
Sakurai had a flippin seizure over Geno's arm cannon, despite being featured on multiple characters already so I'm sure he won't discard Meowth for being vaguely similar to Knight.
Meta Knight seems more like a wall/tornado of slashing hitboxes, which helps him with edgeguarding whereas Meowth would have more diagonal blitzes to make him scratch all around the battlefield, being more focused on keeping the opponents within his reach and on-stage all the time instead of going for "that one push" to edgeguard conversion like how Meta Knight shreds his foes.
Yes, they share slashing, but even on a basic gameplan level they can be miles away.
Same with Corn and Marth.
Corn wants to keep the opponents within optimal range for combos whereas Matth wants to keep the opponent away at the optimal range to force them to the ledge or off-stage.
Same visuals, same moves, whole nother gameplan
Now the question is whether "hyperactive scratches" dances enough, but his chances stand on them own and don't hinge on Meta Knight at all
I hope those scratches can either pierce Defense, because I'm about to Wall you off with all this text otherwise.
Geddit because that was a competitive Pokemon joke ehue
Meta Knight's "that one push to edgeguard" is universal across the roster, you know. Any character can ledge-trump and Meta Knight doesn't even get a Meteor smash to use for said edgeguards. Meta Knight is much more about bait-and-punish, using his quick movement speed to close gaps and quickly get in an attack between an opponent's attacks. This includes several specials which give him offensive movement options and, yes, focused on keeping the opponents within his reach on the stage. The only time Meta Knight's keeping you off the stage is if he's edgeguarding or performing a stairway combo. You're otherwise stuck on-stage with him until the right percent.
Likewise, Marth and Corrin are both zoning characters but go about it in entirely different ways. Marth requires fundamental spacing ability to optimize damage by hitting with a specific hitbox on the tip of his sword. The Marth will always be trying to keep the opponent in a very specific distance away from him. Corrin on the other hand takes towards a much more distant approach, using the sheer range his dragon-limb attacks offer and the projectile of Dragon Fang to outright play keepaway while pressuring the opponent to approach. His combo game isn't as strong and has a closed in damage floor and ceiling as a result. I don't even
know where you're getting "same moves" from, since a moveset consists of more than a counter. Not even getting into the aesthetic difference of the characters (Dragon-parts are the same thing as holy swords? Okay...?), Marth and Corrin very little in common.
I don't know how much Smash Bros. you actually play, but I'm picking up very little mechanical understanding of the game... Either way, I'm not saying there's an entire basis of Meowth not getting into Smash because of Meta Knight at all. That's straw-manning my argument. I mention Meta Knight as a mere example of what I'm talking about for Smash as a whole:
other characters and how their existence makes Meowth itself that much harder of a sell.
Okay, overview of Meowth in the Pokemon games. Looking at Meowth, we have a Normal-type with poor stats and hard to translate-into-Smash abilities in Pickup, Technician and Unnerve. It has no alternate forms, no exclusive Z-moves, no signature items, nothing mechanically to make it stand out aside from Pay Day, which already encompasses what it's capable of as a Pokeball Pokemon. All that leaves is its Dex information, which is all just "it likes shiny and round objects" without the slightest bit of exaggeration. As far as Pokemon go, Meowth leaves very little to work with outside of using scratch attacks and
something to do with coins.
So then, that puts us in a position of, if we are to make a moveset that stays true to Meowth's character and powers, would primarily consist of quick, short-range and often multi-hitting standard attacks a la its scratches. That not an unviable basis on its own, but then we get into how there are other characters that already take up a similar style of gameplay. Your Meta Knights, your Diddy Kongs, your Pits, hell, even your Pikachu--a lot of the gameplay concepts Meowth can explore have already
been explored. Multi-hitting attacks that promote bait-and-punish, rush-down, and/or aerial combo attacks are what all of these characters already have in addition to some of them having similar body builds. It's for the same reason that Chrom was rejected as "just an inbetween of Marth and Ike", because Meowth itself will likely just end up as an inbetween of some of the aforementioned characters. Do they specifically scratch to attack?
No, aesthetically they aren't the exact same. Do they already cover the various aspects of a character whose only battle-relevant powers are scratching?
Absolutely, his gameplay does nothing to deviate himself mechanically.
So where does that leave Meowth if he can't mechanically stand out from the cast? If the answer is creative liberties and making the character just a vessel for a moveset that isn't even core to who they are, that's the sign of a character that doesn't "dance", and something Sakurai is going to avoid like the plague. With the creative liberties taken in Smash, characters at least generally play as a fluid translation from how they would in their games. If Meowth doesn't have a solid
concept, not an
aesthetic, to look at as the basis of his moveset's design, he's not going to be a viable addition to the cast.
tl;dr
"Hyperactive Scratches" is the exact same case of "Tomboy Flower Power" and "Marth but more like Ike" topic with Daisy and Chrom several pages back. Even if a moveset can exist of them in Smash, if it doesn't translate to what they as a character as specifically known for in the games, it's no longer
their character. If staying true to their character likewise offers very little to the roster, then they're probably not a character that should be added in the first place.