Our first RV trip... we decided Colorado?? Must see what???

Off the beaten path is an area of Colorado that meets your criteria and has less people now than 100 years ago. Highway of Legends/Highway 12 West from Trinidad Colorado.
You can choose to stay at Trinidad Lake State Park or go on up to Monument Lake or even higher up to Bear Lake You would be boon docking at Bear Lake.
Monument Lake and Bear Lake and its neighbor Blue Lake are stocked lakes.
If you like hikes check out West Spanish Peak