When you ask your question you ask it generally as if there was only one zoo. There are many zoos just as there are many hotels, bars or restaurants. Some are good and some are bad.
There again what one person sees as a good zoo is not necessarily the opinion shared by others. Some like to get their photos taken with baby tigers etc. I believe it is wrong. The cubs should be with the mother.
I could ramble on. Please look through my zoo hubs.
contamination? stagnant? I am with you. Confined? Well maybe not. It is a territory issue.