This is what I thought of too when looking at the first few images. How can they "walk" in those places?.

However, I believe not all of the examples were steep stepped or cobbled but had vehicular access and were level, and the article explains issues about access and ambulances etc - it would work out fine - arguably better in terms of human closeness.

Motorized wheelchairs is what's mostly used in these cases.

The only examples you see are centuries old. There is no reason why you couldn't bild something accessible today.