I think it depends on the individual zoo. It's up to them to take part in conservation programs or to stick to keeping animals exclusively for display.
The one where I live has historically been a bunch of very desolate animal display cases, but they've committed to doing what amounts to a slow U-turn, and they have done quite well in that regard.
The old enclosures were clearly built to keep animals in plain view at all times. They've remodelled a lot of them since, and they're completely rebuilding some. There are times where you don't see a single great ape during a whole visit, because their new habitats have some caves and comfy areas hidden from view, with the result that especially the gorillas now appear to have quite a bit of fun interacting with visitors at the four separate points in their enclosure where that is possible and definitely seem much more relaxed than the previous generations (as far as I can tell, I'm no gorilla myself).
Certainly still worse than a life in their natural habitat, but they are part of a multinational conservation project and all their current gorillas were essentially sent to them via this project, with the end-goal of (as I understand it) having a viable captive gorilla population in zoos around the world so there is a "backup" in case the natural populations collapse. The living conditions they provide have earned praise from experts (for what that's worth, seeing they're not gorillas themselves, either).
They still keep their lions in a tiny, cruel pen, but they're building a new one currently that is supposed to be state of the art. Most monkeys have gotten new accomodations last year I think and they're pretty involved in keeping Kunekune pigs from going almost extinct a second time and they're breeding Visayan Warty Pigs (which are absolutely amazing things, and critically endangered); I guess for a relatively provincial central European zoo with a limited budget, that's quite decent.
They've also recently completed a pretty big section with heirloom breeds of common farm animals and they do a lot of education programs and events for schools, which I feel is something my generation missed out on big time, not necessarily from a zoo, but some kind of getting in contact with animals other than the occasional cat or dog might have been quite helpful. I feel there are some really weird misconceptions about animals that are pretty widespread among people my age.
For what it's worth, I've been quite opposed to that zoo in the past, but their efforts over the last decade or so have been enough to convince me to pay for a year pass. Some zoos are much slower adopting this approach, I surely wouldn't be as supportive of one of those.