Corals are in decline all over, and I have seen no indications that divers are even a small part of the problem. My first dive in the Keys was in 1976 during Spring Break from UF. Things are different there now, just as they are on Coz, but they are still worth the time and effort. Moreover, I like how we are recording the reef for posterity with all our diving.
Attitudes and situations change over the years. My first pair of fins, bought in 1969, were sold with the caveat that I "could kick the crap out of the reef and not hurt these fins". Most of the changes we need to make are not in the water, but on land. Single use bottles, too much paper & waste, gas guzzling cars, allowing global warming to rise unchecked and more all contribute to a change on our reefs. Many of the fish and corals we know are destined to go extinct and some in our lifetime. They will probably be replaced by new, more tolerant species. Nature doesn't mind the heat like we do.
So don't waste time: go diving. Whether it's in Coz, the Keys or my beloved caves, Get out there and experience how the other two thirds of the world lives. Don't stick with only one place either. See as many different places as you can. Yeah, yeah, Coz probably doesn't like me to suggest other destinations, but you owe it to yourself. Check out Belize, Saba, Fiji, the Philippines, St Anthony's Key, Curacao. the Socorro Islands, Mar de Cortes and I can't list all the places I've have dove. They're all different. They're all phenomenal for different reasons. Yeah. Don't listen to anyone who discourages you from diving. Go dive.