I also don't own a Steam deck and have a good PC with a curved screen. And for couch co-op even a 4k projector with a 100 inch screen.
But I definitely understand that there are uses for being able to take all your games with you and play them anywhere. I already sit at my desk for hours at work.
Of course, it depends a lot on the genre. Competitive FPS or RTS I would rather not play on the small screen, but games like Dave The Diver, Dredge or Balatro sound perfect to me.
I'm sure you're referring to these Opalithplättchen, aren't you?
Impressive that you could remember the name. I'm German and had to look it up since I never heard about Opalith before.