Late September used to be a great time to hit the National Parks and Monuments. Not so any more. 15 years ago visited Capitol Reef in late September and it was not crowded. This year it was jammed and we bailed to a remote FS campground (closed, but no gate).
We did, however, have some very nice compensation. We visited Death Valley NP. It was just 2 weeks after it was reopened after the floods, and while only a few roads were open, there were no large crowds anywhere. There was easy parking at any of the stops. Texas Spring campground had no more than a dozen campers (less than 5%)