I have asked questions on repositories, more times than I have fingers. I have created pull requests that fix problems I've had, fewer times than I have fingers. I can think of twice those have yielded positive results: one time I received a clear answer to a question which solved my problem; another time a pull request was rejected with an explanation. (It was a fair enough reason: my change would have broken a different use-case I hadn't considered. I used my code fix locally - on a personal project - until I stopped needing that project.)
Far, far, far more often than that I have seen my questions already asked, or pull requests already created, with no answer or merge forthcoming. I'm not intimidated by the process, but have come to think of it (on GitHub, at least) as fairly pointless, and it's been ages since I've bothered. (I've also come to avoid using GitHub projects with a single developer, and /or without a really active and recent update history.)
I understand why "I've made the code public; I don't owe anyone anything else; fork it if you don't like it" is a prevailing attitude amongst GitHub project creators. I also think it obviates the original premise of GitHub - to create collaborative communities of developers and users - to the platform's detriment. It's not surprising (but still disappointing) that people are looking to other platforms for the community-development (in both senses) that GitHub could, and was intended to, support.