OSS can build truly incredible libraries and frameworks. User facing products? ehhhhh not so much.
GitHub has gotten worse over the years but it's not like there's some gold standard open source alternative. And remember, early GH was filled with a pretty amazing group of developers and open source advocates.
If the counter is that, instead of buying github, we could have invested in building some other tool, well, that's not how this works. People need to build what the company is actually building for its users.