I found though my reading and other research that most of the structures did seem to focus more on preservation. Some would do annual maintenance , celebrations to pass down traditions, or rebuild the entire structure. Along with restricting general citizen or tourist usage or not allowing it at all.
Modernization seems to be updating with modern amenities such as electricity, HVAC and toilets, which some have not done to maintain historical integrity. Most of the modernization that has been done is a way for the structure to be turned into a tourist attraction to obtain funds to aid in preservation of the structures.
I had the same idea about modernizing these sacred locations. In fact once I read yours I was worried ours might be similar. I think the idea of using these locations as a learning tool is a fantastic idea. I, on the other hand wish each location had a museum-like building in which they could state the history of it all. Along with how they plan to preserve the place. Great job I like your idea that modernizing is just adding amenities not removing anything that isn’t modern.