I knew most characters but there were a few that I hadn’t heard of before they joined Smash. Heres the ones I can think of off the top of my head:
Marth
Roy
The Ice Climbers
Mr. Game and Watch
Lucas
Alph
Alex
Others I was vaguely familiar with but only at a very surface level:
Ness
Richter
Isabelle
The thing with Eevee is that no one has come up with a good moveset idea for it, it's certainly possible but we have yet to land on a winning formula that highlights Eevee itself. Get a good moveset out there and you'll be able to sell it better because honestly? The reasoning for why Eevee should make it is more cynical than Sakurai being given a selection of Hot New Things and being able to pick the Hot New Thing That Actually Appeals To Him. Meowscarada can appeal by being a Trickster "Magician" Cat. Quaquaval can appeal because Carnival Dancer Duck. Gholdengo can appeal by being a Surfer Dude Made Up Entirely By Coins. Tinkaton can appeal because Unga Bunga Hammer. Iron Valiant can appeal because Killer Robot With Energy Dual Blade. Annihilape appeals because Local Ape Literally Too Angry To Die + Gohan Beast. Ogerpon can appeal because Unga Bunga Club And Masks. Baxcalibur appeals because Ice Godzilla. There's inherent gameplay hooks and base concepts here that you can start building from really easily if one so desires.
Moveset Ideas are the key for Pokémon. What can Eevee bring to the table that few other viable candidates can? Provide a satisfactory enough answer to that and you'll start to win people over or at least get people to give it slightly more consideration. At the very least you'll fair much better than lashing out over it for the umpteenth time.
Sell us on Eevee without taking a dig at anything else or shut up is effectively the long and short of what I'm saying.
I think the best way to do Eevee is to base it off its Let’s Go Eevee moveset. That Eevee had a ton of exclusive moves representing the different elements it could evolve into. You could even add a bit of visual flare by creating a spectral version of that evolution behind Eevee when it uses the corresponding attack. It would mostly just be a visual thing and wouldn’t affect the move itself. This could call back to Eevee’s Z move from Sun and Moon (Extreme Eevoboost). That Z move could also work great as a Final Smash. This way, Eevee could still reference its evolutions without having to actually evolve mid battle.
Here’s a basic description I found online for each of your partner Eevee’s exclusive attacks. There’s more than enough to work with here for a really unique and interesting moveset (the attack names are really dumb, I know lol):
| Move | Power | Type | Effect |
|---|
| Bouncy Bubble | 90 |  | Heal for 50% of the damage dealt |
| Buzzy Buzz | 90 |  | Always cause Paralyze on hit |
| Sizzly Slide | 90 |  | Always cause Burn on hit |
| Glitzy Glow | 90 |  | Creates Reflector that halves Special damage dealt |
| Baddy Bad | 90 |  | Creates Reflector that halves Physical damage dealt |
| Sappy Seed | 90 |  | Plant a HP leeching seed on target |
| Freezy Frost | 90 |  | Resets all Stat Bonus for all Pokemon on field |
| Sparkly Swirl | 90 |  | Heals ally's Status Effect |
| Veevee Volley | Varies |  | Power changes depending on Friendliness, never misses |
That said, I’d still rather have Gengar if we get another Gen 1 rep but I do think Eevee has potential to be interesting. Since we’re on the topic of people not sharing their favorite Pokemon often enough, here’s my top three favorites from each generation again (with a couple bonuses). Lucario would be in the Gen 4 section but I’ll leave him off because it already made it into Smash:
Gen 1: Gengar, Electabuzz, Kabutops
Gen 2: Houndoom, Gligar, Sneasel
Gen 3: Zangoose, Seviper, Deoxys A
Gen 4: Toxicroak, Gliscor, Garchomp
Gen 5: Cofagrigus, Zoroark, Kyurem
Gen 6: Clawitzer, Noivern, Malamar
Gen 7: Golisopod, Lycanroc MN, Salazzle
Gen 8: Orbeetle, Toxtricity, Corviknight
Gen 9: Great Tusk, Ceruledge, Lokix
Other: Sneasler, Hisuian Zoroark
and 
