Hey man, I’m not trying to “side eye you with an article”, and I’m happy to let you pontificate as to where the series should go (even if I think you are making sweeping assumptions based off a single comment in an interview). You seem to be very passionate about the series, and maybe you have a lot of insight I’m lacking. It’s possible that you are spot on, and that trying to make a “melee” successor would do as well if not better.
That being said, it’s been repeatedly reported that Ultimate was a staggeringly massive project, so when he says he doesn’t see how it could increase in magnitude, it’s fair to take that at face value as him talking about increasing the amount of content. And it’s fair that if anyone knows the likelihood of seeing another jump of this magnitude, it would be Sakurai. You are free to be an incredulous arm chair game designer, but it kind of just comes across as whiny and entitled.
I also can’t agree with your claim that Sakurai doesn’t know what keeps people coming back to Smash. Ultimate is the most financially successful entry in the series history, selling 31.7 million copies (dwarfing the 2nd place entry Brawl’s 13.32 million copies, and the critically acclaimed Melee’s 7.41 million copies). So focusing on content quantity seems to have paid off for Nintendo. At least it shows that the focus on “bigger” didn’t hurt people buying Smash, even if you don’t think it will have the long term sustainability that Melee did. And when you are trying to make money selling games, hours played is less important than dollars made. source
To add to that, Ultimate had an average play time per copy sold of 88+ hours at the release Sora (obviously it is likely that this is higher now). So your previous claim that “people aren’t liking it” seems a bit misinformed. source