Certainly zoos can be very depressing places, it is a matter of putting yourself in the place of each one of the caged animals, because nobody would like to be locked up or limited to a small extension of land. As mentioned in some of the articles you quoted, zoos become places for the protection of those species that are more vulnerable to extinction, even these places can serve as genetic banks, the problem is that many times it is very difficult to replicate the proper habitat of each animal, there are even zoos that do not even have how to take good care of the animals. It also happens that many times the business behind them is observed, this is very unfortunate.

On the other hand, there are also cases where the captivity of certain species is necessary, an example can be seen in Colombia, where drug traffickers brought a lot of exotic species from Africa such as hippos. After the fall of drug trafficker Pablo Escobar, the hippopotamuses escaped and adapted to the environmental conditions of Colombia, the worst thing was that they reproduced in large numbers (among the family) and damaged their genetics. Now the authorities do not know what to do with them, they cannot return them to Africa because they are no longer species that belong to that continent, so they can carry new diseases or damage the genetics of the species there and put them at risk of extinction, in Colombia they became invasive species because they could not move them all to the zoos, being the size and aggressiveness one of the causes that complicate their transfer, not to mention the enormous costs that this would imply. If people would become aware and avoid indiscriminate hunting, destruction of ecosystems and all those things that endanger animals, then zoos would not have a valid reason to exist, since there would be no species to preserve. Excellent analysis @agmoore, it has been a pleasure to read you.