Buildings with flat roofs and piss poor drainage in the West of Scotland (rains a bit) are held up as timeless paragons of the style.
This tells me there is a massive disconnect between architects and normal people.
(EDIT: There is quite a lot of Brutalist stuff I like but there is a lot of shit decaying ruins that I'm repeatedly told are brilliant that are most certainly not)
Having spent time in quite a few 'iconic' Brutalist building, my experience is that they're frequently terrible. Impressive looking, but deeply unfriendly to their inhabitants. There's one where it sometimes rains indoors because the venting and vault-ceilings are so poorly executed. It's still lauded as great architecture.
Well, on the other end of the scale we have McMansions[0] - although part of the critiques[1] also feel like architect snobbery to me at times.
1. Badly-designed and badly-built (as in, objectively not up to some verifiable standard) homes built with the look of better-built homes but none of the construction quality those homes have.
2. Houses built by the newly-rich on small lots, in contrast with the houses inherited by the old money on larger tracts of land.
The inevitable and, perhaps, deliberate conflation between the two senses is pure class warfare, of the "Established upper class striking against the newly arrived" sense.
If you have a different style of window in every fitting without a strong aesthetic tie then you've just raised the build and maintenance cost of the property for no reason except cargo cultism.
I have never been in, nor seen a brutalist building that looked good and was functional. They may exist, but all the examples in my home town (and there are many) are terrible buildings best left in the scrapheap of history.
But, that discounts the thousands of buildings that were built and subsequently torn down because they failed by some metric. The style didn't make them failures; they just weren't good. Brutalist buildings are no exception, they're just more recent and so we have a lot more of the stinkers still standing.
And, we're living in a time where people value the past (even the recent-ish past) more than folks in previous generations. We venerate old buildings, maybe because the pace of destruction and rebuilding has accelerated beyond our comfort zone for change. So, it's likely that a lot of poorly conceived Brutalist architecture will live long enough to be hated. And, it also does seem to be the case that retrofitting Brutalist buildings to suit modern needs and tastes may be more difficult than previous kinds of architecture. The Grenfell tower is a tragic example of that (though one could reasonably argue that it didn't have to be that way...a little more money spent would have saved lives).
I don't know. I happen to be fond of a lot of Brutalist architecture. Not all of it. And, I recognize and agree with many of your points. But, I think there's a beauty to be found in the raw concrete, straight lines, cantilevered elements, etc. of the best Brutalist architecture. I like the design of those decades, in general, not just the buildings.