Many still are, but 70 star offers a lot of flexibility in routing to just pick the stars that are RTA-able.
I'm curious what the A count for RTA 120 could be. TAS is 13x, but humans will need more.
Gamecube doesn't have enough RAM to preload everything at startup like that, you have to go through the menus and pick a game mode and map to load.
Surely if it needed that startup load anyway, then Sakurai wouldn't be saying he turned the license down in order to get players in the game faster. I'm going to trust Sakurai's word here!
Puyo Puyo. The three best games in the series were Puyo Puyo 15th Anniversary, Puyo Puyo 20th Anniversary, and Puyo Puyo Chronicle (25th in all but name). None of these games ever got released outside of Japan, but after the crossover did well overseas there were high hopes in the community we'd get a similar mainline game for the series' 30th anniversary.
I wrote a very long essay about how that didn't happen, and the state of the series ever since. And a more recent followup video on Sega's newest blunder.
Pannenkoek does have a few videos documenting stars that can be beaten with No Joystick Allowed strats (these are old and there are more on the secondary UncommentatedPannen channel but I don't see a playlist compiling them). A full run is definitely not possible, but at least some stars are doable.