"I don't know much about X, but I know what I like" is a phrase much used by the general public in discussing everything from clothes to music including architecture, unfortunately. But the elements of 'fashion' and 'style' have nothing to do with whether the subject of the vitriol is well designed or not. It is that issue that people have difficulty with. The bus station in Northampton was demolished because it's style was out of fashion not because it was badly designed. All it needed was a clean and the lights turning on and updated to 'daylight' LEDs! Victorian buildings, as a style, were much derided in the 1960s for much the same reason, whist now even poor examples are retained because fashion has changed back (as it does, in cycles).
Buildings today are considered appealing if designed in a 'Victorian' or a 'Classical' style but they are often badly designed and dysfunctional. Prince Charle's Poundbury 'works' as a well designed place but not for the reason he thinks it does, the 'classical' styling. It 'works' because it is laid out for humans not vehicles and is therefore a pleasure to walk through. Recently a house designed by a non-architect was much praised and exhibited for it's 'classical' styling yet was a bad design for many practical reasons: Every toilet was mounted on an internal wall leading to unpleasant sound transmission and the bathroom window (for stylistically reasons, presumably) was a large clear glazed window facing the street etc. Why? there are countless similarly silly errors in non-architect designed homes around the Country. Why?
Many Planning Committees are also unable to distinguish between good design (a planning matter) and mere style (NOT a planning matter). Why?
I am of an age that my tutors and lecturers were heros of Brutalist Architecture which we, sort of, fought back against. But with the benefit of hindsight I can now see that whilst 'out of fashion' in the 1980s, 1990s, and 2000s, many examples were actually well designed. Robin Hood Gardens and Alexander Road in London for example. in fact they were very well designed just neglected, under maintained and vandalised. Patrick Hodgkinson's (my tutor) Brunswick Terrace, after he was allowed to finish and complete it as intended recently before he died, is now a wonderful piece of Architecture, the fact that it was well designed from the start proves that.
A building has to be designed well for a life that may last centuries, fashion and style are irrelevant in the long run. Demolishing a building just because it is not liked is unsustainable. Demolishing a building because it is badly designed, as long as it is being replaced by a well designed one, is on the other hand sustainable.