House value is impacted by the year of construction, and construction standards differ decade on decade. But not in a linear way like the older the cheaper :) The main differences between 1930s and 1960s house is the room location, size, shape - people had different standards of where kitchen should be and how large it should be throughout 20th centry. It is not that the house from 1930s is constructed worse, than that from from 1960s. Just differently.
It is a matter of taste and many people look for houses from specific parts of the century with authentic details. (For some reason, "authentic details" for many people here means pre-war, because after war the rush to build new housing meant identical apartment blocks with less detailing)
Quality does not degrade, as long as houses are kept up to date.
Ridiculously thin walls are problem in all dutch housing - I have lived in houses from 1700s, 1930s, 1960s and 1970s. All the same.
The main factors that impact the price are location, state of the house, shortage (you're looking in a large city by dutch standards). Year of construction does not come highly on this list. And it is a matter of preference for many. (Obviously, older houses are usually much more expensive, I mean houses from before 1900s, but I think you were not looking into these)