I wanted it to be Shovel Knight or Shantae. Shovel Knight was a massive success on Nintendo systems when it came out and IMO I view it to be a sort of a symbolic representation of Nintendo's welcoming of Indies during the Wii U flop days. I also wanted Shantae since that indie's been on Nintendo systems since the Gameboy Color, which really can't be said for any other prominent(ish) indie on Nintendo systems.
Both those choices didn't make the cut. In my eyes that means that Nintendo isn't really too bothered with having an "indie rep" in Smash Ultimate. There's literally none that are more worthy than Shovel Knight or Shantae, impact wise. Hollow Knight is phenomenal but there isn't a solid prior relationship with Nintendo like Wayforward or Yacht Club Games have with Nintendo. It was just a really great indie that was announced for switch and took a long-ass time to get there.
Idk. I love me some Hollow Knight but I'd get crabby if I find out that Hollow Knight gets in when Shovel Knight or Shantae are still on the sidelines. The indie rep from smash should represent Nintendo's efforts in the indie space in particular, as well as the indie rep having their game on the Switch system. With those in mind, idk of any more worthy than those already included.