A common theme with residential (other types don't have these problems, like museums, public office spaces, hospitals, etc.) brutalist buildings is that they were built as low-cost social housing, and the problems are not with the exterior but with the interior, and I think not inherent to this type of architecture. Shoddy workmanship, cheapest materials, etc. The contrast between how stunning it looks (a matter of taste, granted) from the outside and how it's inside is stark — avantgarde, modern, and bespoke, combined with boring, gloomy and depressive apartment interiors.
A lot of commenters have mentioned New Belgrade municipality of Belgrade, and it is a great example of this. The exterior is very often quite well though out — lots of space, lots of trees and parks, playgrounds (looked at from the ground there's hardly any of the oppressive concrete feeling often associated with brutalism), general living affordances like schools, public services integrated into complexes... But on the inside, even ignoring long term issues of maintenance stemming from broader social issues, things are dysfunctional, ugly and generally of poor quality. It's a byproduct of cost cutting commonly associated with these types of projects. But just like with apartments in Soviet Brezhnevkas and even some Khrushchyovkas, when renovated with care and attention the apartments are just fine for what they are.
And it's not just a feature of Cold War socialist brutalism. In Trieste for example there is a somewhat (in)famous Rozzol Melara building[1][2]. As an idea it's great, the complex has everything for day to day living, a post office, a supermarket, an elementary school, a kindergarden, even a small medical facility, all connected with tunnel bridges or roofed passageways (except the small chapel) so you're never exposed to the elements when going somewhere inside the complex. But it seems as though the architects thought about how can we make this cheap but practical and then got the practical part completely wrong. For example, the passageways and tunnel floors are completely covered with anti-slip rubber matting, but the problem is these passageways are almost too practical and inviting so people end up using them to take their dogs out for walking, and so the result is rubber covered with sticky, dried dog piss (sometimes even poop) every 5 to 10 meters in all directions. You can imagine how this smells, encased in concrete and glass during the summer in a moist coastal city. The terrace views from higher apartments on the side overlooking the city and the sea are beautiful though, so you get some satisfaction if you live in one of those.
A lot of commenters have mentioned New Belgrade municipality of Belgrade, and it is a great example of this. The exterior is very often quite well though out — lots of space, lots of trees and parks, playgrounds (looked at from the ground there's hardly any of the oppressive concrete feeling often associated with brutalism), general living affordances like schools, public services integrated into complexes... But on the inside, even ignoring long term issues of maintenance stemming from broader social issues, things are dysfunctional, ugly and generally of poor quality. It's a byproduct of cost cutting commonly associated with these types of projects. But just like with apartments in Soviet Brezhnevkas and even some Khrushchyovkas, when renovated with care and attention the apartments are just fine for what they are.
And it's not just a feature of Cold War socialist brutalism. In Trieste for example there is a somewhat (in)famous Rozzol Melara building[1][2]. As an idea it's great, the complex has everything for day to day living, a post office, a supermarket, an elementary school, a kindergarden, even a small medical facility, all connected with tunnel bridges or roofed passageways (except the small chapel) so you're never exposed to the elements when going somewhere inside the complex. But it seems as though the architects thought about how can we make this cheap but practical and then got the practical part completely wrong. For example, the passageways and tunnel floors are completely covered with anti-slip rubber matting, but the problem is these passageways are almost too practical and inviting so people end up using them to take their dogs out for walking, and so the result is rubber covered with sticky, dried dog piss (sometimes even poop) every 5 to 10 meters in all directions. You can imagine how this smells, encased in concrete and glass during the summer in a moist coastal city. The terrace views from higher apartments on the side overlooking the city and the sea are beautiful though, so you get some satisfaction if you live in one of those.
[1]: https://www.greyscape.com/architects/rozzol-melara-trieste/ [2]: http://architectuul.com/architecture/rozzol-melara-complex