It's true that a lot of aquaculture is not great environmentally. There's a spectrum.
Two points though.
(1) Even some of the worst practices are at least relatively localized. For a given tonage of fish, commercial fishing fleets affect far larger areas, with the most productive areas usually most affected. I think practices need to improve a lot, but even with the current below-par methods... Imagine a ranch with terrible environmental practices. They indiscriminately poison predators, overgraze, use bad fertilizers, run effluent into streams... That 1,000 acre ranch is surrounded by 100,000 acres of wilderness (or good tree farms). The ranch is bad, but enough wilderness can dilute its effects.
(2) A lot depends on the species of fish. With land agriculture, we tend to farm a handful of species that lend well to farming. Before farming, people ate different species. Still, agriculture didn't produce bear meat, otter or some other hard-to-raise species to suit the preferences of hunter-gatherers. With aquaculture, we're still often trying to farm otter and bear.
Tilapia & carp (for example) have a long history of aquaculture. It's cheap and efficient and can be done in environmentally sound ways. The problem is that salmon (raised in environmentally unsound oceanic pens) sells for 5X per kg.
To me that means regulation can be sharp. If salmon, cod or tuna are replaced by more agriculturally enclined species... that's a reasonable compromise, IMO. We can have fish, just not any fish.