Since the general consensus especially among lower skilled and more casual players seems to be that individual performance doesn't matter and you'll get an even 33/33/33 ratio (I've read it on those very forums too), even if thinking this is completely unhinged or uninformed, I do wonder if it would just make your "leechers" not bother and continue afk-ing in FL all the same by justifying their decision with this kind of rationale.
Furthermore, they could also be very aware of their lack of skills and could very much think that whether or not they do actually participate changes nothing in the final result, and that they'll be happy to let the competent players carry them.

You can call me jaded I guess but I don't think your solutions are actual solutions. Just live with them, and report if they bother you. The real solution is GMs that actually do their jobs.