I think as most people moved to using a phone as their primary computing device (no HNers, you're not most people), the size pretty much settled on 6-7" as being in the best range to accommodate what people use them for.
I call it the Grandma Test. Within reason, whatever my grandma is currently doing or capable of using on her devices is “the norm.” if she struggling to do it, then it’s not mainstream. There’s obviously exceptions to this rule, but it’s been working pretty well for me.
I think the joke was "people discovered we could watch porn on it", but you're on to something. Streaming media on a phone or gaming is viable for most urban/suburban areas so most people can get by with just a smartphone if the screen is big enough.
It’s not an original thought, but this a major contributor to the enshittification.
Enshitification of what?
The web, and social media in particular.
The size of phones is a major contributor to enshittification? I don’t understand
No, the majority of people using phones as their only computers.