In my opinion, there is no expectation for someone to accept your requests or PRs. It's definitely not the norm, but I reserve the right to not do anything that I don't want to do. You don't know someone's life situation or current goals; that library or tool may work fine in their use case or they don't have the time/desire to implement a fix or review a PR.
That's why forking exists.
That's the risk of pulling in external libraries from random developers. Unless you're willing to put money where your mouth is, then all you reasonably can do is politely request a fix or for them to merge your PR.