You can build standard games now, and there is a waitlist for Unity Spark. But there are demos of Unity Spark games now, if you want to see what will be possible.

I was able to spin up a couple of games really quickly--a 2D cosy space exploration game, and a snarky sci fi trivia game. I'd say the the writting for the humorous trivia questions and the cosy interactions was reasonable--this isn't a tool that can only do reskins of old school arcade games. In addition to music and graphics it can do text to speech.

It's still an experiment, simultaneous impressive, and frustrating, with rather unexpectedly low prompt compliance. But, beta.

It really doesn't seem to like shifting from multiplayer to solo play. It seems like you ought to have a strong opinion upfront. (again, early days)

It's natural to think of this quick and easy tool for playing game, but I suspect part of the eventual value will be learning tools and "self gamification" I could imagine doing a variant of my trivial game for memorization or language learning.