Some things change, others stay the same.
In 2003, I did the rim to rim run with a small group from Austin, TX. The NP discouraged these activities to the point that we talked little about what we were doing. Now it is so common they are charging fees.
We trained for it, much as one would in a "build" for a marathon complete with downhill repeats to prep our quads and knees for the first 7 miles to get down to the bottom of the canyon. We saw many "casual hikers" who appeared to be no more prepared than those taking a walk in a city park. We heard the stories about the number of rescues the park service and emergency response teams would have to perform.
I don't recall trash (litter) being a big issue, but each of us picked up what we saw, left the canyon a little cleaner than before we entered.
To run it again and have to pay the fees? I wouldn't be mad about the fees, I would be mad about those who are unprepared for the conditions or for those so clue-less to leave the litter for others to pick up.