I feel like I'm not even speaking english on this thread. I've said MANY times that project owners owe nothing to anyone, period. You don't owe anything. Ignore the PRs, send them to your junk folder. I don't care.
That has nothing to do with this discussion.
People have a right to propose changes to broken things they use. Your right to ignore them and not provide support is a two-way street. Others also have a right to ignore what you want and propose changes for other users to see.
it's right there is name of the feature "Pull Request", it's a request, not a demand.
If you were operating a non-profit business in person, you can't get mad at people suggesting changes either. You can ignore them for sure, you can pull up some disclaimer or whatever. But it's hostile and mean to prevent people from even stating their opinions and proposing a change.
At that point, make your project private.
You don't owe the public many things, but when you create a project and make it public on a shared hosting site, other users also have rights to make commentary, since you've exposed it as public, and proposals and to assist each other. I'd even go further to say that this counts as intentional interference with users' attempt to fix vulnerable and buggy code, and as such an intentional attempt to harm the public. It's one thing to not guarantee anything about your software, it's another thing to prevent people from trying to fix it.