I suppose you might be right, but I definitely don't feel that way myself. If it wasn't for GitHub, I don't know if I would've made an effort to get involved with the projects I use. It's made it insanely simple to find a project, get documentation and a list of open issues in one place, with a consistent UI across projects. It's also been a pleasure committing fixes for projects I use - as mentioned above, being able to discuss the fix in a code review style environment, with the original author is hard to beat.

Projects I've published myself have been a breeze to maintain, because pull requests are really easy to manage. I can review changes with the submitters, pull the changes myself to tweak if I need to, and auto-merge when changes are simple enough. It also acts as a nice portfolio for potential employers.

I guess I feel like OS in general is benefiting from the likes of GitHub, not suffering. Just my two cents.