This is my feedback on using GitHub to manage a popular project (ESLint). Topics are presented in no particular order. In general, everything I say about issues also refers to pull requests.
For each problem I've suggested a solution. I realize that actually building out a solution is a complex process and my suggestions do not reach the level of detail sufficient for implementation purposes. It's just to give you an idea of the direction I'm thinking.
Users are opening new issues every day, and these issues automatically bubble to the top of the issues list by default. We do label issues that we're committed to doing as "accepted", but if there are enough new issues, you don't even see those until the second page of issues. Why is this a problem? In a word: distraction.