I don't think banning cetacean captivity would doom the aquarium industry.
Aquariums don't need dolphins, but dolphins need aquariums. As I told before, entertainment industry could profitably produce animatronic and VR entertainment focused on mermaids, krakens and pirates and get rid of all live animals. The loss will be conservation awareness.
Only one particular example is aquariums recently raising awareness of disapperance of vaquita. No aquarium critic organization does so.
Is there any evidence of this?
Yes. Read history of cetaceans keeping, and compare public awareness of related sea mammals which are kept in aquaria and those which are not.
It has been known since Antiquity that dolphins are clever. However they were seen simply as another fishing resource. The dolphin-mania in the West started only in the 1940s with aquaria, when the public could see dolphins interacting with people, either themselves or on the screen (Flipper and numerous followers).
To this day this public interest is limited to dolphins in aquariums only. Can you put a query of dolphin or killer whale on Google Images? 90% to 99% of high quality photos, those on posters and calendars, will show dolphins in aquaria.
Then do you know how these animals look like:
ringed seal, southern right whale dolphin and
dall's porpoise without searching? Everybody knows californian sea lion, bottlenose dolphin and killer whale. But the first three are equally widespread, small sea mammals. All three have very attractive shapes and patterns. But they have been never exhibited in aquaria, so don't exist in public knowledge. How many already knowledgeable people on Zoochat know all three?
Here you see: small cetaceans only exist in public imagination because of aquaria.
On a side note: there is a good opportunity to make a zoochat thread with a photo quiz - "name that animal".
Which is ironic: animal rights movement kills its own base by acting to eliminate dolphins from aquaria. But a parasite often kills its host. I see animal rights movement attitude to aquaria as parasitic: they suck money generated by public interest in aquarium animals but contribute nothing to wild conservation.