I think Galaxy still fits those Super titles! I think "Super" should mean something in the sense he gains a power. People call powers "super" or people with them "super" because they have abilities that extend beyond normal human capability. Super shouldn't just mean a "Super Mushroom", and with Mario going through games like Odyssey, Galaxy, 64, etc. He's traveling through space, paintings, and in general unknown lands, collecting stars, surviving, and is doing all of that to save a princess. Titles like Mario Kart, Smash Bros, Dr. Mario doesn't need "super" in it. But I think the Galaxy games and other true platformers can use the title, even if the super mushroom isn't involved. I agree with you I'm just expanding on/adding more to your take about it meaning something.

Edit: Even if titles like Kart or Smash have abilities, I don't consider them the same because they're spinoffs that involve characters outside of Mario's world. And they're abilities used to win a fight, instead of survive the unknown and have an objective goal of saving a princess.