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.