I think they solve different problems. Gogs is amazing for a self hosted git repo. Not so much for collaborating with thousands of people around the world. Centralization can be a very good thing if done by an ethical company with the right incentives. The only reason decentralization is useful is when you can't trust anyone for anything. I'd rather live in, and work towards, a world where that's not the case.

But some (like Gitea) are working on it to start hosting it on their own. Gitea will also get federation features to make contributions between independent Gitea instances possible.

But even when it starts to host, it will get GitHub OAuth2, just to keep the barrier small to receive contributions.