It was my understanding that had changed at this point. That most networks have the support but still prioritize v4. Is that incorrect?

The only time I ever have working IPv6 is when I'm using the cell network. No place I've worked, and no place I've lived, has had working IPv6. I'm in Oslo, Norway, so not exactly a technological backwater either.

Most consumer devices today use some variant of the "Happy Eyeballs" protocol that prioritizes v6 to one extent or another, but "races" them (if IPv4 is faster to ping for a given DNS host it switches to IPv4 for that DNS host; otherwise it prefers IPv6). Things like NAT and CGNAT naturally slow down IPv4 so many consumer networks very heavily prioritize v6 in the "Happy Eyeballs" races.

I believe Windows with Hyper-V (used for WSL 2) actually prioritizes ipv6 over ipv4 even. Not well, mind you, but that's a different story.

I use one of the largest ISPs in the US and it does not support IPv6.

I live in New York and neither have IPv6 at work nor at home.