Lab grown fish are one thing, but simple fish farms already work really well, the issues are that the fish don't eat a natural diet and are sicker and less healthy to eat. Maybe that's an easier problem to solve than growing fish meat in a lab.
It still means deforestation, biodiversity loss, soil degradation, poisoning the ecosystem with pesti/herbicides and fertilizers on land (with the associated runoff into the waterways) and a lot of organic waste on the water (each salmon farm in scotland produces as much organic waste equivalent to a town of between 10 and 20,000 people each year).