A slightly related question, if anyone knows - has phone GPS gotten worse in recent generations? More reliance on local wifi networks or something like that?

I ask because I do a lot of backcountry hiking, camping, and foraging and rely on true GPS-only navigation. My most recent two phones (iphone and pixel) have noticeably worse GPS performance than previous phones, and I even changed OS ecosystems mostly hoping for better GPS, but it didn't help. Maybe I've had bad luck, but two noticeably bad phones in a row seems like it may be a pattern.

And is there any way to find phones with very good GPS performance?

I don't know, but I have noticed that the GPS in my watch (Garmin) seems to be better than the one in my phone.

Aggressive battery saving, thinner phones, competition between multiple radio transceivers in a small device - these can affect GPS performance.

Try disabling battery saving measures as much as possible and see if it helps.