V interesting and as others have stated, a difficult subject.
Over the years I have visited quite a few zoos and "water park/aquariums"..off the top of my head, in a vaguely chronological order:
-London Zoo when I was knee high to a grasshopper.
-Ocean park in HK - there was a killer whale.
-Longleat.
-Paignton zoo when I more than knee high.
-A French aquarium, near St Malo (ish?)
-An aquarium in Vancouver in ~2012ish
-Durrell "zoo" in Jersey
-Plymouth aquarium
London zoo I only really remember a nellyfant frisking my dad's pockets for peanuts and wiping it's trunk on his nice beige jacket he was wearing.. and a gorilla vomiting then eating it again... I was probably not massively aware of the concept of captive animals at that stage.
Ocean park in HK, again I was young and in awe of the killer whale, but retrospectively I dislike the captivation of those beasts!
Longleat I recall enjoying a lot, I liked seeing the animals off doing their own thing.
Paignton zoo I remember being more aware of the conservation side of things at this stage. The zoo itself highlighted it's reasoning for having a rhino and all, but again I still think I was a bit shocked by its small enclosure.
The French aquarium I recall was mostly just fish.... Interesting to view.
The Vancouver aquarium made me disappointed in the "advanced" world... In fact Vancouver and I guess Canada on a whole, I felt had some catching up to do (puppies in shop windows n all). But the aquarium I wasn't keen to see a beluga whale backing and forthing in its tank, again, impressive to witness the amazing creature, but it didn't feel right to see it in a tank.
Durrell zoo in Jersey was something else actually. It was founded by Gerald Durrell who (if anyone has watched the series on TV) grew up in Corfu and as a little boy was fascinated in animals and wildlife. Their ethos seems to be more focussed on the small animals that no other zoos tend to care about. That being said, they did have an orangutan or two that were looking a tad moody the last time I went there. But the whole place is done very nicely and it's pretty quiet all round.
Plymouth aquarium, again, fish n the like, but there is a turtle in there that looks a bit fed up... Just goes round and round and round.
Not what you asked for granted but that was my thoughts on the matter at the time.
From a wider point of view, they definitely do help to generate interest in wildlife which can in turn generate money for the animals and can inspire young uns to pursue conservation careers... So that's all good... But then again, if I was stuck in a cage with thousands of screaming children banging the glass every single day, I think I'd try and figure a way to get out and eat one...