There is a genus of South Pacific snails,
Partula , that was endangered ( severely so in the case of some individual species ). Captive breeding, and cooperation between many zoological societies, has increased the global population, worked with local people to preserve and improve habitat and successfully reintroduced species to islands and atolls on which the snails had become extinct. Without Meerkats and other species the public considers 'cute' enough to cough up the entrance fee in order to see there is no way finance could have been raised to accomplish something like this. Admit it, would you donate towards saving a Snail? The zoo workers that carried out the captive breeding and much of the ground work in Polynesia, have accumulated a wealth of knowledge they wouldn't have had and a whole genera has been brought back from the brink. As has been said before, it's not a case of good or bad. Anyone who is really concerned about animal welfare should be putting their energies towards improving the conditions in zoos, and supporting the expansion of scientifically based conservation strategies based on captive breeding and reintroduction of endangered species. Calling for the abolition of all zoos is throwing the baby out with the bath water and, in many cases, detrimental to the very existence of some species.
As for replacing the word "zoo" with some more 'customer friendly' / 'touchy-feely' euphemism? I won't give my thoughts on that as the mods will do a bit more than shout at me.