Not sure I agree with your belief that there's been a move away from these sorts of facilities.
Grandiose public (or foundation-backed) "serious" aquariums in the style of Shedd, Monterey Bay or even Vancouver aren't exactly popping up like mushrooms. I'm far from an expert, but the only one I'm aware of that's been built in the last 20 years in North America is the Oregon Coast Aquarium. The existing "serious" aquariums are certainly making a point of reinforcing the distance between themselves and the Marinelands of the world, yes, but that's hardly a new phenomena, and that's very different from seeing new-builds.
You're right to point out that entertainment-driven fishhouses like Ripley's aren't the same, er, kettle of fish, but it's not as if Toronto was really facing a choice between one or the other. One type is self-financed by the private sector, the other tend to need public money or substantial charitable giving. Toronto was only going to see the second kind if (a) the federal and provincial politicians decided to reach out to the all important seahorse-fancier vote and lavish huge public dollars on one, potentially through Waterfront Toronto (and, no doubt, at the expense of some other public amenity improvements) or (b) David Thomson had a secret sea otter fetish.