The parks this year were nuts before it closed but the 2018 average attendance for the entire year was almost exactly 50% capacity for the resort; higher that 50% at MK and AK, lower at Epcot and DHS. They've done such a good job of Spreading out crowds over the year with pricing that the parks essentially never have capacity closures that last more than a few hours anymore, and even those are basically just a prohibition on off site one day ticket entry.
Believe it or not, it can be a LOT busier! That’s why capacity limits are more realistically going to start around 15-20%. And they’ve said they don’t expect to make money at first, just to lose less than they’re losing now.