I will say, the fanbase IS more inclusive to non-Nintendo series than it was during Wii U or 3DS. But I personally think there's still work to be done. I understand that most of the Smash fanbase is made up on Nintendo fans. But being a Nintendo fan doesn't mean you can't also be a fan of other incredible non-Nintendo games.
This.
You can be a Nintendo fan and at the same time, being fan of other platforms such as Playstation, Xbox, PC, or a fan of multiple third party companies and non-Nintendo franchises. Metroid Prime is probably my favorite game of all time, DK Tropical Freeze's probably my favorite 2D platformer, I play Smash and visit Smashboards frequently, Fire Emblem is one of the series I've played the most in the recent years, I spent hundreds and hundreds of my life playing Pokémon Emerald when I was younger...
At the same time, Playstation consoles are the platforms I've spent most of my time playing, I'm a Final Fantasy nerd, Halo 3 was one my top games from the previous generation, God of War 2018 is probably the best game I've played this entire generation, my childhood was basically Crash Bandicoot, Sonic and Ratchet & Clank, and I don't want to remember the insane amount of hours of Tekken 3 that I must have played back in the day.
I don't think there's nothing wrong to prefer certain genres or consoles when it comes to gaming. I won't force people to play games or buy consoles for the sake of it. Each people is different and the same for their tastes and interests, and it's okay if you are only a fan of 3 franchises. No one's saying that you must try and be a fan of every game in the world to be a true gamer or something like that, because playing and be aware of every franchise is virtually impossible.
I just think that the point is, there's a lot of cool things in this industry, in every platform and in every genre. If FP7 is, idk, a character from a point and click game (a genre that I've barely played) I won't be upset, I'll probably start looking for info about the fighter or their series because I wanna know more about him. Not knowing a character is completely fine, but at the same time it costs 20 seconds to use Google and do a quick research.
Spamming "literal who" and "no one knows him, give me [insert popular request that probably is only relevant to core Smash/Nintendo fans]" like happened with Hero or Terry is just being obnoxious and proud of your lack of both ignorance and ability to open Google and write a name.