Josh from EasyWDW breaks down the numbers:
Overall, FP+ is causing wait times to increase at most secondary attractions, while having a less substantial impact at the most popular attractions with the longest wait times.
That seems about right. People who never would use a Fastpass on a given attraction are now being forced to select 3 attractions a day, causing those extra attractions to get long waits. Hopefully, the next phase of Fastpass+ can help alleviate this problem.