On "purely rational, economic grounds," it's possible a great many memorials and monuments might be removed or demolished. But I'm not sure that a dearth of public appreciation should be a primary reason for doing so. If that were the case, then some of history's important events may no longer find any representation in the public sphere.

This does raise a serious question, however, having to do with the relevance of specific memorials and at what point they may cease to serve a useful purpose. Most often, memorials are removed or destroyed when changes in political circumstances alter the memory culture they were meant to represent. The most obvious recent examples would be the numerous Marx and Lenin statues and other socialist sculpture that disappeared from various locations thoughout Eastern Europe after the end of the Cold War.

Should expiration dates be applied to public monuments and, if so, how are we to determine what those should be? Should removal be approved by simple majority vote? Or does respect for minority interests require that, in some (perhaps many) cases, monuments be maintained, even when the bulk of popular opinion wishes them removed? It may be easier, in a certain sense, to determine when a monument is no longer appropriate. But is it as easy to decide when one is no longer relevant?

There seems to be much room for opinion and discussion here.