Are you looking for reasons why I think they're of no value?
First, even the name itself is highly deceptive, not sure if that's on purpose on not. People post questions about a crowd calendar, wondering how crowded a park is and how accurate the crowd calendars are. They then rely on these crowd calendars and even avoid certain parks simply because they think a park will be crowded. However, in the fine print, they even say they don't actually predict crowds. They try to predict wait times for a ride, which may or may not have anything to do with a crowd. To me, it's a bit of false advertising, especially for those who don't look at the fine print.
So even putting that aside, they look at historical wait times. Ride wait times are subject to so many variables that the ride time from 8 Thursdays ago at 3:25pm is utterly irrelevant to the wait time next Thursday, or the same Thursday in 2019. They can be effected by staffing, mechanical or guest issues causing the ride to stop, weather, or just random variations in people going for a ride. It also is effected by people adding and dropping FP+, which happens literally every second.
Put all that together, and my opinion is that they're completely useless.