This is how I mostly feel these days, aside from Nintendo taking full control of the characters back then. It's important to remember that Nintendo took most of the money from SMRPG's development back in the day. Nintendo really didn't seem to respect other developers so much before Satoru Iwata took over and mended relationships with them starting with the GameCube era. So with that lens in mind I'm glad Square was able to secure a large part of the game's appeal all to themselves, away from Nintendo's at-the-time thankless attitude.
Of course, THESE days it's a different issue. It's pretty baffling that Square Enix has done practically nothing with the SMRPG original characters they created and has just collaborated with Nintendo to re-release the game on various systems instead. This is the biggest contributing factor why I feel so bad for Geno hopers, it seems like their character may never get into Smash because if Nintendo owned them, they most likely would be in right now, but since Square Enix owns them, then it has to be tempered with "Well, it wouldn't be the best business decision for the company," which majorly sucks.
I like to think that Nintendo and Square Enix have "made up" in a sense, since the game that marked Square's decision to switch consoles is finally coming back to a Nintendo console, and because we're getting all these ports of FF games that were exclusive to non Nintendo systems in general, and because ever since 1997 the two companies have collaborated on things like Mario Hoops 3 on 3 / Mario Sports Mix / Fortune Street on Wii.
Wouldn't a new project with Super Mario RPG content, or just content in Smash, be a great final bowtie on the two companies having patched things up?
So yeah, I'd be ecstatic for Erdrick but if it somehow means that Geno or Mallow or anyone else from that game won't be in Smash, it'll be tempered with a bummer kind of vibe.