Actually, there are some awesome MTB/eMTB rides in Colorado and Utah that are on "dirt roads". Almost all of the original MTB rides in Moab, the ones that made it famous, are on what are considered to be "dirt roads". Porcupine Rim, Amasa Back, Gemini Bridges, Hurrah Pass, Poison Spider, Klondike Bluffs, Monitor and Merrimac, etc. Even Slickrock is actually a motorcycle trail, and the parallel 4x4 trail called Hell's Revenge is considered to be a "dirt road".
In CO, the 4x4 roads west of Central City and above St. Marys are fun.
Gnarly 4x4 roads are awesome on an MTB and an eMTB makes them even better. Less pushing.
I wouldn't call slick rock a dirt road but to each his own. I live in Utah. Riding behind Razors making clouds of dust is not my idea of fun. I've actually ben stuck behind large atv "tours" on my ebike in Moab. It sucks and the extra sand on the chain wears out the drive train quickly. Much better to ride my moto on that stuff.
If you don't like sand, I don't know where you ride in Moab other than above the Loop Road. The place is made of sand, after all.
To each his own. Most of the "classic" Moab trails (the ones in "Above and Beyond Slickrock") are open to ebikes and a ton of fun. The riding was awesome last weekend. It was almost like the old days, you could ride for hours and not see a soul.
If you were riding Moab last weekend then that is the off season. You probably won't find much moon dust this time of year. I guess when I see the word dirt I actually think of real dirt. You guys seem to think a road that is 90% slick rock is also called dirt. Oh well. I just don't consider something that can be ridden while it is raining a dirt road. Semantics....