At the moment the IPv6 adoption is around 33% globally, meaning every 3rd ip address in use is IPv6. There are several countries with close to 50% adoption or somewhat above that already. Comcast and AT&T reached 50% IPv6 adoption 2 years ago, Comcast is at 70% now, AT&T is at 75%. Are you suggesting that half of a country like the US can't access Twitter?twitter.com not resolved with ipv6
Here's a nice website to check the status of popular web services.
https://ipv6.watch/
If it's the case, the possible explanation is that ISPs provide IPv4 addresses as fallback to IPv6, otherwise it would be impossible for half of the US and 60% of India to access Twitter, because IPv6 adoption is quite mature there already.host twitter.com just return only ipv4 addresses, there is no ipv6 in list. and no need to mention any services. or in other words no DNS record for ipv6. how you going to access it? lol