As one of the few who actually quite liked FastPass+ when I visited WDW in 2019, I will be sad to see it go.
However, I can certainly see the benefits of a paid system from a logistical standpoint. It will likely reduce the amount of people using FastPass, therefore meaning that it will have less of an impact on the main queue, and it also means that Disney can regulate its use more effectively, so that the number of FP users is never too excessive. So from that standpoint, it should improve the park experience!