Might it be worth implementing some sort of "minimum" standard for what types of routes should be included?
I know some of the MT secondary highways are gravel, but most of those I've driven have been acceptable. Same with the western half of Montezuma Canyon Road in Arizona, though the rental Toyota Corolla might not have been the best choice there.

Perhaps signage is not enough when considering "roads" that are not official at the state level or above. Could be a topic to discuss further.