There is debate to be had on both sides. I'll play devils advocate for a moment. Its hundreds of years of scientific knowledge on the QT of humans and livestock (mammals) the first public aquarium opened in may of 1853 and they certainly didn't have coral or qt the fish. So we don't have hundreds of years research with captive care of fish let alone QT on them. These fish spend their whole lives swimming in parasites ever see an analysis of the number of parasites in seawater? Why is it that when they're put in much more sterile conditions that we find it prudent to medicate them? The stress from shipping sure but how often is an aquarist buying a freshly imported fish? Theres a chain of custody before reaching the point of sale. If a fish is immunocompromised due to stress from shipping why in the world would we expose them to further stress with medication and an unnatural environment like a qt with no rockwork?The question shouldn't be about if you are "for" or "against" QT, or even if you believe it works. There is no debate on whether or not QT works, hundreds of years of general scientific knowledge and principles confirms that if you properly quarantine a fish that came thru a shipping channel riddled with parasites and diseases your chances of introducing a deadly pathogen to your existing system go down dramatically.
The question should be:
Do you care enough about the animals you are keeping to go thru the trouble of educating yourself on proper quarantine processes if you plan to not limit yourself on where you source your animals from OR are you willing to only source animals from captive breeders or from a dealer that has a satisfactory quarantine process which will likely cost more?
There are *for sure* people that haven't quarantined and haven't had any major losses, some even over many years, but that should not be construed as evidence that QT is not needed.