I tend to lean more towards what the animal experts and doctors, many with degrees in the given subject matter are feeling on a topic in terms of the effect on animals. In our growing society, some ecosystems are being swallowed up entirely, or due to changes in climate, what once was hospitable, is no longer capable for animals. In the case of flamingos, I can't ever recall from my own experience, remembering seeing them indoors. When a flamingo decides to fly, they can really fly. That may make aviaries difficult for that given group of species. Looking at a flamingo, or birds of that size, I'm not sure what could be the best practice in terms of handling them. Whereas I know netting can be used, the bird could just as easily get it's wing caught in the netting, like manta rays do in the ocean. As weird, and possibly wrong as it might sound, it's possible they don't want it to fly, because it would get injured, and possibly in a far more life altering way. The debate will be, if this is the best we can do, should we continue to keep soaring birds in captivity. That's a question for society though.
Animal Kingdom does have some of the obvious headlining animals, however it also is lacking quite a gfew as well. Some I'm sure simply due to the idea they don't think they'd be able to properly care for one. AK has no species of bear, and until recently, had no dogs until the painted dogs were added. I don't think Disney has any poisonous snakes. Marine life is basically only seen at the Seas. Lots of zoos have animals that were injured in the wild an are unable to go back into the wild. Some were born there. Lots of zoos have far more animals behind the scenes then they do actively on display, as sometimes they are caring for animals that aren't too photogenic, or active during the day, but are still looking out for them. Some have them for breeding programs, but only a few are on display as the others are off exhibit.
I was not really aware this practice took place, but it may be the only way to have soaring birds that are capable of large scale flight in captivity. That being said, if other options were presented, and they were better for the bird, I would hope we'd as a society lean towards that. Earlier I talked of the need for zoos and aquariums, and I think it is true, as for many, it actually is the first time they can see an animal like that. The sad reality though is, for animals that are possibly every bit as endangered, society doesn't band together to help out, because they don't even know such a thing exists. They know of the headliner from a given family, like they'll know what a monkey is, and maybe even some species, but not the majorly obscure forms of monkey. I think though zoos help with that, as at one's local zoo, they can be exposed to animals that other places might not. a gharial is a member of the alligator/crocodile family, and has needlenose snout for fishing. Sadly, people haven't been exposed to it enough to even know it exists, to have the drive to save it.
My last paragraph was a bit of a jumble, but staying on the topic of flamingos, there are multiple species of flamingos in the world. Much of society looks at flamingos as all being the same, so whereas, (I'm making this part up, I'm not looking it up) for the sake of discussion lets say the lesser flamingo was massively endangered, but the greater flamingo wasn't. As long as one iconic version of the flamingo exists, to a lot of people, it's fine. That's not true, or accurate, but it is a view some have, as they oversimplify the animal kingdom. As long as the common gecko, chameleon, komodo dragon, and a handful of others are okay, most assume all lizards are fine. That of course isn't the case, but the general public doesn't even know the other lizards, so sadly there isn't much for them to miss.