Unfortunately this is not true, loads of cool techy stuff (Sentry, GitHub) etc still don't work properly on IPv6, less techy stuff really didn't care at all.

You can use nat64 to talk to legacy networks. Ipv6-only networks (with nat64 or 464xlat etc) are becoming increasingly popular. There is also this new concept called "ipv6-mostly network" that is getting rolled out: https://www.ietf.org/archive/id/draft-ietf-v6ops-6mops-02.ht...