You are saying EVERY single Waluigi supporter out there wants him just for the sake of memes?
Le bias
People who generalize that all Waluigi supporters wanted him just for the meme are wrong, because some people do have a genuine emotional attachment to the character.
But those people are very few in number compared to the droves of people who do indeed just want the character for the meme. How often do you see people making reasoned and well-written arguments for the character's inclusion compared to people just shouting "WAAAAA" or making joke pictures?
Compared to most other characters that people request, who do so because they have a genuine emotional connection to the character for one reason or another, Waluigi is one of the more superfluous. He's not too far from Shrek in that regard.
You'd be surprised how many people throw out Geno because he's not REALLY that wanted or something like that.
Actually you probably wouldn't lol.
Geno's fanbase is a bit more than a vocal minority at this point imo
It's hard to tell who is and isn't a vocal minority these days. As discussions get spread across more and more platforms, getting a pulse on who's really requested is difficult. You've got Twitter and Facebook, Reddit, GameFAQs, SmashBoards, YouTube, and more. And really, people like us who discuss the game online are the vocal minority with regards to the fact that most consumers don't really engage in these discussions online to begin with. That's why character polls are so unreliable, because there's no way you can reach everyone.
Ridley and King K. Rool aren't popular with a broad audience, because they only appeal to the older, core audience who are fans of Metroid and Donkey Kong Country. Relative to the requests of the broader, complete audience, anime characters like Goku would be more popular than Ridley or K. Rool.
The ballot occurring in 2015 when Nintendo and the Wii U were not in the broader public consciousness probably made a huge difference regarding what characters were added. The hardcore audience were the ones paying attention, while most gamers were paying attention to Witcher 3, Bloodborne, Until Dawn, Metal Gear Solid V, etc.