Git is a distributed VCS just like fossil. GitHub never has been an integral part of it; it's just the most popular hosting option. This is like saying you're glad you're using Firefox because everyone complaining that Twitter is down is using Chrome.

Even if you do just GitHub for hosting you can, on account of it being distributed, still work and commit code.

What is more disruptive is that so much code is hosted on GitHub that even if you're not yourself hosting anything there, you risk almost all your dependencies being unavailable to your build pipelines. If you didn't have a cache set up, you're gonna have a bad time.

Too much of their process it's tied in with GitHub. That's what people are complaining about.