In regards to the "Gaming Hall of Fame" mindset, I think people latched onto this because it's been such a focus on the advertising of the game. Sakurai said "Simply put, this is the biggest crossover in Gaming." in the 2018 E3 direct. Reggie at the 2018 Game Awards said that Smash Ultimate is "Dare I say it, the biggest crossover ever." And Sakurai throughout this whole DLC cycle has stated that there is unlikely to be another game like this with so many different franchises. This has pushed a mindset that Ultimate is about expanding the crossover. We hear things all the time like "Wouldn't it be cool to see Dante in this game fighting all these gaming icons" or "How sick would it be to see Bill Rizer fight Samus" things of that nature. It also doesn't help that after this game, it will be much harder for many characters to get in. Newcomers will be competing with veterans. Sakurai might want to prioritize bringing back Mega Man and Ryu, instead of making Phoenix Wright a new fighter. With this in mind, I completely understand this mindset. And honestly I'm a part of it. While I am open to characters from preexisting series like Kirby, Metal Gear, Mega Man, Xenoblade, etc. and there are several characters from this category I support, I do prefer if characters from completely unrepped series gets in instead. This might be the only time we could see Dragonborn fight Joker for example, or Isabelle fight Doomguy. In a lot of people's eyes, this game is giving their favorite character the best chance they probably will ever have.
Of course there are plenty of great options from preexisting series. Alucard, Bandana Dee, Dixie Kong, Zero, Chun-Li, SNK characters like Geese or Kyo, Raiden, just to name a few. And they do have good reasons to be in the game. But while we have every single veteran in the game, it would be nice to see new faces from brand new series while we have the chance.