...I actually kind of like Meowscarda. At the very least, I do think holding it against Meowscarda for not being the most conceptually interesting option theoretically possible is a bit unreasonable. Sakurai's relationship with the TPC is different than his relationship with Nintendo. He doesn't seem to have the luxury of being able to pick random curveballs like R.O.B or Piranha Plant. Smash will always consist of Pokemon that TPC is interested in as a product (Jiggs is a grandfathered-in exception that would have fit at the time), it will always be Pokemon that have prominent in-game roles, prominent anime roles, lots of merchandise, etc. Could Great Tusks or Tinkaton be more interesting than Meowscarda or Quaquavel? Sure, but Great Tusks and Tinkaton don't really have any path to entry into Smash and I don't think laying that at the feet of Meowscarda or Quaquavel is particularly fair.
I think a lot of Meowscarda's appeal is that it is a Pokemon with a realistic chance of inclusion that is very easy to imagine in Smash. It's fast, oriented towards physical offense at the cost of defense, and attacks using claw swipes, plant manipulation, and status moves like Leech Seed and Trick. Those gameplay features all sound very at home on a Smash character. I also know "lol grass type starter" is memed on a lot, but there's a reason it's been a complaint for almost a decade now. Agrokinesis has a lot of potential for fun scenarios, but it's still unrepresented in Smash beyond Ivysaur and Piranha Plant. The odds of us getting such a character outside of a Pokemon is relatively low, so grass-type starters tend to attract genuine positive attention beyond just filling out a quota with Greninja and Charizard/Incineroar.