Marine mammal and shark aquaria represent a small minority of aquarium applications, except for the top 1% category for volumes. And even out of those, quite a few do not cater to the public for entertainment value. That's also not including rehabilitation and/or breeding tanks.
Unlike decades earlier, a large proportion (if not majority) of today's captive marine mamals were born and raised in aquaria, and could not be reasonably educated to live in the wild if released. Behaviorally those specimens can be classified as domesticated. In such cases having the critters do backflips to pop music isn't really that outrageous at all.
For most captive large aquaria animals, their lifespan greatly exceeds that of the wild. This isn't the technology of the 1960's and 1970's anymore... for the most part anyway. Today's facilities and husbandry care are pretty dang good. Diets are specially made and delivered, exotic-animal vets are on call, water quality is computer controlled and monitored, and tank designs facilitate low maintenance and animal health.
It's rare nowadays for marine mammals to be captured for aquarium purposes, unless they are injured or very rare. In both cases capturing them either helps them, or the species. Myself, I've helped capture a couple dolphins for such purposes.