I don't know, maybe I'm not getting the sudden looping back to "Nintendo legacy".
Everytime a non-Nintendo character joins Smash we get some folks saying, "Ah yes, of course! We didn't predict that character, but they were obvious because of their clear Nintendo legacy!"
The first 3rd party we got was because of business relations, sure. Sakurai was close with Kojima, and we get Snake. However, Nintendo execs were actually unsure about adding Snake. He wasn't added because of Nintendo legacy.
Sonic wasn't added because of his "Nintendo legacy". He's ****ing Sonic the Hedgehog. Mega Man is largely Nintendo, but alongside Castlevania I'd say it has more to do with having that retro legacy that, obviously did take place on Nintendo consoles. Despite that though, both series have had a widespread affect on the industry as a whole. You don't have games like Shovel Knight, Celeste, or Hollow Knight without Mega Man and Castlevania.
Pac-Man is ****ing Pac-Man, has little if anything to do with Nintendo connection. Ryu is Ryu from Street Fighter.
Cloud is quite literally the Final Fantasy character most related to Sony, just like Joker and Snake are more seen related to Playstation. Final Fantasy is largely known as a top tier JRPG series. I would more believably go with the Nintendo-connection argument if the character were most "Nintendo"-like.
I would keep going, but it seems like folks wait for characters and then try to find ways to make it about Nintendo, when it just...doesn't seem to really be that way. There are connections everywhere, but after all...Sakurai is a "Student of gaming history", not just Nintendo. To make everything about how it relates back to Nintendo seems to sell things short.