I don't think any of the sites really know what the crowd levels will be on any given day as we are still in uncharted territory. Only Disney knows how many park reservations are gone for each park on any given day and they aren't giving out that information.
The sites such as Allears that post wait times can be useful.
But there are so many variables. Do they stop the rides and clear cars - depends how long the ride is down. How many cars do they have going, what their staffing level is. All of these things have a huge impact on our waiting time, maybe more than how crowded the park is on any given day.