In 2018 we drove through Monument Valley (amazing) and on to Tuba City - less than amazing. So much so that I told my husband we should cancel our 2019 bike ride through the area as there is a whole lot of nothing but wind out there. End of story is that we did ride through and it was wonderful at 10 mph. So much so that in 2020 we bicycled Mexico to Canada through the Rockies (and Monument Valley again).
A big consideration for us was how hard Navajo Nation has been hit by COVID. It is impossible to bicycle Arizona without riding through Navajo Nation, it's too large. Currently they are having weekend long lockdowns and nightly curfews to discourage travel and spread of COVID. Be aware that camping is allowed only in certain areas and by permit only. It is wide open country. You need to plan water/food/lodging carefully. The area was magical - we rode through two years in a row, once each direction. I would go again.
Your trip route covers an excellent cross section of the USA. In Colorado, after Independence Pass/Aspen, I would suggest: Redstone, Crested Butte, Gunnison, Lake City, Del Norte, and then head west. That would give you an intoxicating about of mountain vistas before you hit the red rock areas.