I whole-heartedly agree. Wildlife isn't some magical thing that keeps existing, no matter how much you build around it. I've been to a handful of Asian zoos now, but I've never seen a snake or monitor in any of them besides Singapore. The fact that many reptiles are still so easy to see on the grounds of Singapore Zoo means they make an effort to keep the environment inside and next to their exhibits natural, with many native plants to make sure there is enough reason for the wild reptiles to stay. The same is true and can be seen with birds in multiple examples - I saw a lot more wild birds in Toronto Zoo, Zoo Plzen and Safaripark Beekse Bergen than in most other places. This is not because those zoos have a better location than others, but because they make excellent wildlife management decisions and keep a lot of true nature within their boundaries.
An interesting point that I don't think has been brought up is also the amount of rescue animals Singapore Zoo receives and releases back into the wild - in this category it is particularly noticeable with
reticulated pythons. Both Singapore Zoo and the Singapore Night Safari are designated wildlife rescue centers.
Singapore Zoo is also very involved with other conservation purposes, as can be seen on the website and on many articles - two examples are programs for
Roti island snake-necked turtle and
Singapore freshwater crabs.