Don't say, "ruin it with my attempts at adding details." Instead, think of it as trying out different ways of adding details, and then discarding the ways that don't work.
Honestly, speaking for myself, I have to "try out" different ways of depicting things on EVERY map I make. Even the one that just won last month's challenge. I draw something (like trees, or fences, or windows--jeez, the windows...), look at it, realize it doesn't seem quite right to me, and then retrace my steps. I erase and draw again. Sometimes a third time. Sometimes I look around at the work of other illustrators to see how they solved the same problem. Finally, I'm able to produce something that looks "good enough" to stand on its own so that I can move on to some other aspect of the map.
Those are the skills you need to develop: the ability to try something, erase, and try again. The willingness to look around and try to figure out how others have done it before. And most crucially of all, the ability to walk away from one part of your drawing, feeling satisfied that it's as good as you can make it (right now, with your current skill set) so that you don't get bogged down and exhaust yourself on details that don't matter. So that you can move on to other parts of your drawing and finish them up. Yes, finish. Finishing the project, even if it's not perfect, is essential for growth. You learn more about your process every time you have to push yourself to complete a piece.
Working digitally can help with the erasing, of course. I work mostly in ProCreate, which gives me layers, undo's, blending modes, etc.