I understand the desire of some to return to the more relaxed pre-FP days, but make no mistake: The elimination of traditional Fastpass in exchange for Fastpass+ is NOT going to reduce overall wait for standby guests! Fastpass+ has not increased ride capacity. All it is going to do is spread out the waits more evenly across attractions, and make it more difficult for anyone to visit a headliner more than once.
With regard to the headliners, we have no reason to believe that the same number of Fastpasses won't be available for any given day as are distributed now for traditional Fastpass -- in fact, the flexibility of choosing a time may make Fastpass+ even more popular than the original Fastpass. If they're not all reserved for a given attraction on a given day, it is possible that the standby wait might decrease a little bit, but that's the best case scenario, and an unlikely one. Most days, the same number of people will be going through the Fastpass line as before. Meanwhile, the standby lines for most OTHER attractions are going to increase, because many of them will now have a fastpass line for the first time, which will slow down the standby line and create an artificially high demand for attractions that used to be walk-ons. In other words, you may now get to wait for Big Thunder Mountain for 35 minutes instead of 45, but you'll be squandering that saved time waiting in longer lines for the Haunted Mansion, Carousel of Progress or the Tiki Room.
At best, standby-only guests will now wait longer (because there will be Fastpass lines at more attractions slowing them down) and Fastpass+ users will break even (waiting less for 3 attractions, but waiting more for the others). Those who used to make good use of Fastpass will fare much worse than before, since they've lost the ability for multiple fastpasses and/or multiple headliners that they had under the old system.