reminder: most maintainers of open source software are unpaid volunteers who are stressed out, and showing up in an old issue just to say "why haven't you fixed this" only serves to demoralize and frustrate them
in addition, if you're not an existing contributor or a domain expert adding new key insights on the problem, it's incredibly unlikely that your drive-by comment "solving" the long-standing issue is any better than saying "why haven't you fixed this"
On the other hand a workaround for other users with the same issue is pretty good, I can just mark that shit as read and not do anything else. A pull request is actually *less* value at that point, because PRs are lots of work even when "perfect" (and none are, really).
Yes, chiming in with workarounds is great. I also agree a PR is not an awesome slam dunk good thing to provide, especially when it comes out of the aether. Ideally you would first take the time to express intent to fix it, and discuss your strategy in detail with the maintainer