At Moab, we've stayed at Spanish Trail Campground ( https://spanishtrailrvpark.com )and liked it. It is convenient to Arches and Canyonlands. At Capitol Reef, we were looking at Wonderland RV Park in Torrey, but we had to cancel. http://www.capitolreefrvpark.com
Ruby's is nice near Bryce ( https://www.brycecanyoncampgrounds.com )
Don't know what to tell you for Zion. I know there are some that are supposed to be pretty good, but I haven't been to any of them.