a) open source developers are obligated to provide their users with fixes to any bugs they run into, or
b) open source developers will never ever do anything for their users, so anyone who uses open source needs to be competent at maintaining and modifying all the open source software they use.
I hope you don't truly believe that, and assuming you don't, I hope you aren't arguing this way in bad faith.
Because neither of those things are true. Open source developers will often want to fix bugs in their software, and add new features that people find useful. A user need not assume they'll have to take ownership of everything they use and maintain it themselves. But an open source user has no right to demand anything from the developers. Sometimes the user will have to do their own work if they're having a problem, because sometimes those problems won't get addressed (either ever, or on a time scale that the user needs). And anyone who makes use of open source software should go into it with that understanding.
I've done that myself: I've adopted open source libraries at work (and for personal projects), have found issues with them, fixed the issues, and sent PRs to the maintainers (and maintained and used my own forks until those PRs were merged and new releases made). On occasion when bugs I've found seemed like they'd require too much deep understanding of the code, I've filed issues and provided as much information as I could to help the maintainer reproduce the issues. Sometimes those bugs got fixed, and that's great. But sometimes they didn't. That's frustrating, to be sure, but those maintainers had no obligation to me. From there, I had three options: a) dive in and take the time to learn the software well enough so I could fix the bugs myself, b) live with the bugs being present and decide that that will be ok, or c) drop that software and find or write something else that met my needs.
And all that above is what you sign up for if you decide to depend on someone else's open source work. If you don't like that, then you have two choices: a) write everything that you need yourself, or b) pay someone else for their work. That's it. You have no right to demand anything from any open source developer.
For any project that I maintain... anyone who comes in believing I'm obligated to do whatever unpaid work they want from me immediately gets banned from whatever communication channel they're using to make those demands.