Let's look at he 5 freedoms in that document. How can we address them?
1. Freedom from thirst, hunger and malnutrition(by ready access to fresh water and a diet to maintain full health and vigour)
Okay. Research and choosing appropriate foods for how our fish have evolved. Water changes on a regular basis, something many aquarists still debate. Working to gain a basic understanding of biology.
2. Freedom from thermal and physical discomfort (by providing appropriate environment including shelter and a comfortable resting area)
A difficult one, as it necessitates massive reductions in how we stock tanks. Far fewer fish, but larger single species groups for shoalers.
3. Freedom from pain, injury and disease (by prevention or rapid diagnosis and treatment)
Another difficult one, as it would require training. The hobby approached this in its past forms, as many aquarists were really good on diseases as they were understood. That may be the biggest change I've seen in my 60 years of fishkeeping. We have unlearned.
Now, as the complexity of the issue has become obvious, we've dropped the past knowledge and have run for the hills. It's all the cycle and API test kits, right? We no longer sit and study what fish diseases are. Bacterial infections, parasites, viruses - the general knowledge among hobbyists has dropped radically.
As well, we have the factory farm model of fish production and distribution. That works against disease control and fish health.
4. Freedom from fear and distress (by providing sufficient space, proper facilities and company of the animal’s own kind)
5. Freedom to express normal behaviour (by ensuring conditions and treatment which avoid mental suffering)
I see 4 and 5 as interlinked. They imply the elimination of 'monster fishkeeping' (large fish in small tanks), an increase in tank size and an increase in our willingness to work at our hobby.
Ultimately, the fishkeeper needs to change. We have to reject convenience as a guiding principle. We have to recognize that we need to adapt to their needs, and not the other way around. We need to look at the evolution of fish, and what it teaches us, while looking at the diversity of species. Can we do that?
I doubt that very much.