I think a key problem was even as late as the '80's, with incidents like the Sumatran rhino and Amazon river dolphin, there was still an attitude to acquire a species, place it in a semi-generic exhibit and play it by the vest. Throw the dolphin in the same tank you'd use for another Amazon creature, or let the rhino in a generic paddock with a rainforest-y background - and we'll see what happens.
This is not the same attitude and level of care placed towards more recent and successful attempts at conservation, and in today's day and age, we're becoming much more adept at learning how to take care of these species before they're running around a public yard. More effort can be invested into studying behavior in-situ first and preparing the exhibit effectively.
This is why I'm optimistic about the future of conservation in terms of individual species, and why I don't always take 'this species didn't do well in captivity forty years ago' as the end-all reason - that does
not mean captivity is always the best or only answer either.
Ironically this story is why I am skeptical of captive breeding: as with Sumatran rhinos it gets left... late. It's not as though people hadn't noticed the decline for years before anyone turned to captive breeding. And suppose the captive breeding attempt fails like it actually harmed the Sumatran rhinos.
I would agree completely that it's problematic how often these efforts are simply ignored until the species is as close to the edge of extinction as possible. I think the unfortunate truth is for these less charismatic species, it is often the higher up, larger groups, that refuse to give in to political pressure to assist until it is too late.
As for the possibility of it getting worse, I don't believe it possibly can. If the species is going to become extinct within a few short years in
either case, I think it might be better for them to die in the care of the scientific community. The controversy with the Sumatran Rhinoceros seems to be rooted in the idea they had more of a fighting chance before the intervention than after.