We can't, and that's the issue. There's no fair way of adjudicating which such complaints are true and valid, vs. which are partly true but distorted, vs. which are outright false.
It seems to me that the status quo is the least-bad feasible option, which is why we stick with it, even though of course it has downsides. I still think the Who Is Hiring threads are valuable, even with those downsides, and trying to do significantly better is one of those things it's important to say 'no' to. The problem is not that it wouldn't be valuable—it's that it would be valuable, but would consume too much of our limited resources and ultimately distract from the main goal of trying to run a good (or good-enough) forum.