This number was actually significantly higher and arguably worked better when fp plus was free.
Standby lines for the newest, most popular attractions had become completely unwieldy under FP+. There were reports that upward of 85% of daily capacity had been allocated to FP, making standby a literal crawl. Plus the tiering of attractions and the early booking given to WDW resort guests meant rides like Slinky, 7DMT and FOP were completely off the table unless staying at a Disney Resort.
FP+ worked great if you were spending a week or more at a Disney Resort and could afford to tackle the parks in small bites. You could spread the tiered attractions over several days and still hit most of them. Or locals could visit in short bursts on evenings & weekends, and still be able to hit a couple key attractions with no wait by booking in advance.
It wasn't so great if you were making a 1-day visit to a park, staying off site. And if you didn't have advance knowledge of FP+ or made a spur-of-the-moment visit, it was slim pickings by the time you entered the park and got up to speed.
Do WDW resort guests and other knowledgable visitors deserve the better access that FP+ offered? I wouldn't argue against that, but I'm guessing it was a constant pain point for guest relations and WDW managers.
At the end of the day, they're just doling out resources within a system that doesn't have enough capacity to satisfy everyone. Slinky can handle maybe 15,000 guests on a good day, but there could be 30-40k entering the park. Same is true of Test Track, Rise and other low capacity / high demand rides. There's absolutely no way to accommodate everyone. FP+ and Genie+ are just different approaches to turning people away, with the added fee being the signature difference between the two.
If there's one advantage to Genie+, it's that standby lines aren't nearly as oppressive as they were under FP+. On the most popular attractions, less of the capacity is being dedicated to Genie which means faster-moving Standby. Of course, it also means more people using standby. It's difficult to gauge the net impact on wait time because it ultimately comes down to how many people are willing to stand in that line. There will always be people who draw the line at 30-45 minutes...and others who are willing to wait 2 hours because they refuse to buy Genie or prioritized other passes.