FastPass was a good idea. You're making the line virtual and keeping it in the park.
FP+, not so much. Now you still have a virtual line but you're extending it outside the park and for months.
Regular FP favored park experts and rope droppers so it had its issues as well. When FP+ was announced the threads were filled with people upset they would no longer be able to get 15 FP's a day. The issue is not so much FP or FP+ but the number of rides everyone wants to do and the capacity of each ride. Even if you got rid of FP+ and just had standby the lines for the most popular rides would be almost as long because in the case of MK park capacity has increased and the other parks because the overall amount of rides has dwindled due to closures.