I am not totally sure of the ADA ramifications. It would need a full survey of the existing facilities, which I'm sure someone has done. You are correct that not every area or aspect has to be compliant but on a place that big, it is a big exercise to figure out. Obviously, the big bathrooms in the lower west are not accessible due to the ramp and that would be very difficult to make them compliant. But building new toilets might not be all that hard. The upper north is fully compliant, I believe, but the ADA has requirements that different tiers or levels of experience need to be equally accessible. For instance, if you have Suites in a hotel, some of them must be compliant, not just standard rooms. Same with tiers of seating in a theater.
Also big to note is that the ADA is not a building code but a federal law and the consequences for getting it wrong are potentially large and it is a big target for litigious entities.