Race to the bottom: https://en.wikipedia.org/wiki/Race_to_the_bottom

Related:

Market for lemons: https://en.wikipedia.org/wiki/The_Market_for_Lemons

Adverse selection: https://en.wikipedia.org/wiki/Adverse_selection

Commoditization: https://en.wikipedia.org/wiki/Commoditization

And, as you say, enshittification: https://en.wikipedia.org/wiki/Enshittification.

That's why it's hard to have nice things.