Well said, this is what I was getting at as well. I think the barrier to contribution was too high in the old days, and that is where GitHub brought improvements, but it came with the loss of community. Everything becomes about PR's and Issues and Discussion was just lost. In the Apache community, the expectation used to be that everything had to happen on the mailing list. Even if someone created an issue, there was an expectation it had to come out of a mailing list thread.
I am not saying this was perfect or even better. Just that the side effects were different. Probably a lot of people did not bother contributing because the barrier was too high, but overall I think it created healthier community dynamics and it was not uncommon to see people begin as users asking questions, and evolve into users answering questions and eventually contributing to the development.