Xenoblade is excellent, Metroid is excellent, Kirby is excellent. There are others but those are the primary ones which come to mind for me. Obviously they're all Nintendo games but that's what you get a Nintendo system for. You don't get it because it's the best option for playing third party games.

I've played Smash Ultimate probably more than any other game in my life.

Yes

Baba is You is great if you want additional demoralization

Bought it for 70% cheaper on my phone

Most Japanese video games are designed for solo play.

Maybe that is the case. But when the switch came out the marketing was heavily skewed towards "party" games to play with your friends in the same room.

How is a portable console about playing with your friends? It's about playing alone on the couch, on the bed, on the plane, on the toilet.