Funnily enough, all these constructivist and brutalist buildings are often in practice more expensive than something from 19th century. Flat roof means snow and water accumulate there (because effective flat drainage is expensive to construct and to maintain, so it was skimped) and damages roof and corners. No external rain pipes for the sake of flat facades means rain now falls close to the foundation, freezes and cracks it. No rain covers over and under windows (or too tiny) has the same effect. Oversized windows are hard to do and the seating is getting degraded over time while any maintenance to these flat glass monstrosities is prohibitively expensive. Then during the actual usage the heating bills are enormous while the interiors have freezing temperatures. Flat and blocky balconies and protrusions have the same issues and flat roofs. Saving money on the "invisible" parts like rods inside the concrete causes them to rust, degrade and break (remember Genoa bridge?).

It is already a topic in student textbooks, how the first private villa in the constructivist/bauhaus style was wildly over initial budget and suffered severe degradation even in the first few years, strictly because of the design decisions.

I have worked to repair houses both old and new. You are right about fancy fixtures and whatnot in older houses, but modern construction is problematic also. It seems that houses are never built to be maintained.