I feel like GitHub made a lot of hacking around and software development a lot more seamless too. Before GitHub, the average state of software development seemed a bit more clunky to me.
Github made _Github style_ development seamless--i.e. centralized source control, slick web UI instead of CLI focus, pull requests instead of e-mailed patches. It's one of many different ways to build software though and it's a fallacy to say the entire field of software development didn't move forward until it existed. For someone who has only known Github style development it's true, but for many projects (including some of the largest in the world like the Linux kernel, all of Google's internal code, etc.) Github style development isn't necessary.
> it's a fallacy to say the entire field of software development didn't move forward until it existed
I mean, like, it kinda did in some ways? I feel like GitHub's semi-centralized web UI and pull requests empowered a lot of people to engage in software development online that wouldn't otherwise. I think if it didn't, we wouldn't see value in GitLab and Gittea providing GitHub's accessibility in a more decentralized way.