The perpetual chicken egg problem of IPv6: many users don't have IPv6 because it's not worth it because everything is reachable via IPv4 anyways because IPv6 only service don't make sense because they will only reach a subset of users because many users don't have IPv6.....
I mean, yes and no. For an individual or individual systems? No, it's not hard. But I used to oversee a WAN with multiple large sites each with their own complex border, core, and campus plant infrastructure. When you have an environment like that with complex peerings, and onsite and cloud networks it's a bit trickier to introduce dual stack addressing down to the edge. You need a bunch of additional tooling to extend your BGP monitoring, ability to track asynchronous route issues, add route advertisements etc. when you have a large production network to avoid breaking, it's more of a nail biter, because it's not like we have a dev network that is a 1-1 of our physical environment. We have lab equipment, and a virtual implementation of our prod network, but you can only simulate so much.
That being said, we did implement it before most of the rest of the world, in part because I wanted to sell most of our very large IPv4 networks while prices are rising. But it was a real engineering challenge and I was lucky to have the team and resources and time to get it done when it wasn't driving an urgent, short timeline need.
Honestly this isn't even true anymore. Most major ISPs have implemented dual stack now. The customer doesn't know or care because it's done at the CPE for them.
I use a browser extension which tells me if the site I'm at is 6 or 4 or mixed. In 2024 most major sites support V6. A lot of this is due to CDN supporting it natively.
The fact that GitHub doesn't is quickly becoming the exception.
Globally it's at about 47% and growing at about 4% per year. If the rate remains unchanged it'll be about a decade for >95%.
But the reality of it is, you don't need global adoption out of the box. You just need majority adoption in the countries you visit, which for me are western countries (north America and Europe) which now have a majority adoption.