We went Thanksgiving week in 2018. It was a great trip. The only line we waited more than 30 minutes in was to see Mickey on Main Street. And, we never used more than 3 or 4 fastpasses per day. If I recall correctly, I think the only attraction we missed across all 4 parks was the Nemo show at Animal Kingdom (we were there for 8 days, Saturday to Saturday).
I did an enormous amount of advance planning to have is in the right spot in the right park at the right time to beat the crowds. But, that was the beauty of FP+. It provided the opportunity to secure the major attractions 60 days in advance, and allowed us to fill in the gaps between fastpass attractions in a .logical manner.
Genie+ does not allow for advance planning and is going to have people criss-crossing the park for no logical reason. As a result, I think all the busy weeks are going to be painful to experience until some adjustments are made.