This is not a question of whether or not there should be zoos but what zoos should or should not do with animals that have been kept in zoos for quite some time.
Animals that are no longer welcome might simply be killed.
The Washington. DC based National Zoo, part of the Smithsonian Institute, is closing parts of its zoo due to lack of funding.

“The National Zoo announced Monday that it will shut down its exhibit of invertebrates — water and land creatures that don’t have backbones — on June 22.

The closure of the exhibit, which is in a secluded part of the zoo, is a cost-cutting move, zoo Director Dennis Kelly said in a statement.

Some of the animals — the hissing cockroach, the bird-eating tarantula, the peppermint shrimp, among others — may be sent to other zoos, the zoo said. Some may be moved to other locations in the zoo. Some may have to be euthanized if new homes can’t be found.

The exhibit has cost $1 million a year to operate, and needs an estimated $5 million in upgrades, the zoo said. Its five staff members will get jobs elsewhere in the zoo.

The last day to visit the exhibit is June 21″.