There are two factors at play here I think. The first is that Github has become quite popular. The second is that Github has worked a lot on usability - it's now very easy for users who are not very technical to create an account and report issues.
At times I imagine there could be some kind of "I know how to report bugs"-certification that people could somehow earn. Projects could then use this as a barrier to prevent getting too many useless issue reports.
The problem really goes both ways - as a software dev I'm disincentivized to report detailed bugs to projects, because there's a high risk it will get drowned out in the noise.
Some projects have quite specific templates for reporting issues. This helps a bit, but you still need someone to go in and remove issues that don't match the template, and few people want to volunteer for that work.