The problem is that your users also have limited time and if it's clear you're not even looking at issues where someone has put in lots of effort to help you then you're only going to get lazy issues and it will actually take more effort from you to do all that work yourself if you want to reach the same software quality.

I think you are missing the point: a user putting in a lot of effort into a bug report is usually trying to help themselves get the bug fixed.

As a maintainer, you will obviously look at that bug with more appreciation: but if you estimate it will take you 3 months of active development to fix it that you will have to spread over a full year of your weekends (which you can't afford), what would you do?

And what would a reasonable user rather see? Yes, this is an issue, but very hard to fix, and I don't have the time, or just letting the bug linger?