Disney could open a water park I’m sure but maybe they just don’t think it’s the most pressing thing to open them at this point. Especially if as you say, every other water park in the area is open.
I’m not sure why everyone is so up in arms about them holding off opening a water park. There was a pandemic, not created by Disney.... seems to me like they are doing what they believe is right to keep people safe while also allowing people to still get somewhat of a Disney experience. There are a lot of things to get worked up about in the world , I’m just not sure this needs to be one of them.
They have a huge property. They've decided not to open all of the resorts or the water parks. Makes sense to me. Opening everything at once is a headache. So they picked what they wanted to open. Whether or not it's about staffing, revenue, or what, doesn't really matter as far as I can tell--either way they're still closed. At the end of the day Disney gets to choose what to do with their own property ,and we just decide if we still want to go or not. 
