First off besides maybe one day the Knotts food event sold out on every day except maybe one
Second no theme parks are open 100% open, even sea world which is opening can only have outside shows/exhibits so no rides or shark exhibit even.
Florida parks are no indication of CA, we have 4 million people alone in LA county...not to mention people who will drive from near by states once the parks open.
Third even if you are right and no one wants to show up a new land will change that? No parent is going to be like "ohh Nintendoland is open lets risk our health"
They will either come to a park that will be closed close to a year at the point it opens with basically two new rides...or they don't. Another land isn't going to help them out when its going to cost ALOT to run the new land and have people hired for that land plus everything else but be limited on how many people may enter the parks.