It's ISPs who are the main problem, not applications.
Not software applications, applications of network usage (though I see why it would be reasonable to misunderstand)
Both
Even already, I think you can get away with doing almost everything v6 with a much smaller number of ipv4s for legacy traffic. I say that but still largely use v4 for everything, so maybe I'm not one to talk.
Unless you need to pull anything from GitHub…
Then direct your anger at Microsoft, not Amazon.
Why not both?
Both are dominating the internet-cyberspace and both are screwing it over for everyone else.
Why do you need a public IPv4 address to pull from GitHub?
GitHub has no modern IP support, so a system without a legacy IP is unable to pull anything from GitHub.
That's the idea, you route github through a legacy route and use normal route for everything else.