One of the big motivating factors in the development of git was the desire for decentralized version control.
With GitHub, we threw that away. It's centralized on steroids. Now we're all depending on one platform that has to be massively scaled to deal with the massive load of serving almost every major software project on the planet. And when it is down, we all notice.
I see this repeated a lot and IMO it's simply not true.
The main decentralized advantage of Git is that you can continue to do VCS operations without network access or access to the remote host.
Most of what Github does is managing collaboration. The only thing we've "thrown away" by using Github is the email based workflows or directly pushing git branches to various hosts. But unless you're gonna have team members SSH into each other's machines you'd still need a central repo somewhere.
With GitHub, we threw that away. It's centralized on steroids. Now we're all depending on one platform that has to be massively scaled to deal with the massive load of serving almost every major software project on the planet. And when it is down, we all notice.