If there is a market for “accessible” pools, then hotels would be able to charge a premium for them, which would encourage more hotels to make their pools accessible.
It’s really wonderful how the free market works when it is allowed.
The market only works that way if demand is high enough to justify charging a premium. The whole point of the ADA law is to force businesses to offer amenities that aren’t in demand enough to justify the expenditure. It’s the antithesis of how a free market works.