I'm surprised by everyone's lack of support for this. I used to live in Japan and the biggest thing I miss is sitting in a hot bath (sento or onsen) while watching it snow. I'd rather push to make sure they get this right than hope it fails.
It's not an opposition to saunas or pools or what have you.
It's a combination of things that will vary by the poster; but in general:
Many of us believe that as public land, it should serve a public purpose rather than a private interest.
Many also take issue w/this particular private purpose (indoor tropical beach), on a space that was created to celebrate Ontario, which is not tropical.
Quite a few would say that more of the site needs to be outdoors and accessible freely to everyone.
While there are quite a few who doubt that the arguably most redeeming elements of the proposal from an architectural perspective will come off as contemplated.
Therme, in much of Europe is more a suburban/ex-urban phenomenon akin to Wonderland (indoors) or a super-sized Great Wolf Lodge.
It just seems an awkward fit here.
The parking lot at Canada's Wonderland might be just the spot!