They could have done this by letting resort guests book their first ride only and kept the best parts of genie but instead they now made it the worst version of line skip since its inception
Thats because the new systems (like the FP+ of old) wasn't intended to be a good line skip system.
No matter that Genie+ replaces FP+, at a fundamental level they were NOT the same thing, and didn't have the same goals in mind.
FP+ did several things. First it acted as an incentive to Resort guests, providing a free service that was better then what people not staying on property had. Second, it was a trip PLANNING system not a simple line skipping system. It was a reservation system that let you guarantee you were getting on X ride, at Y time, no matter the what the conditions were day of trip. It benefitted people who wanted to do pre-planning, who wanted to stay on property, but it lacked flexibility to take into account actual lines. You might pre-trip get a FP for a ride on Monday morning, and that day, it turns out the wait is 5min and you didn't need the FP to skip a line.
Genie+ did other things. First it was a day of service, treating day guests and long term stayers equally. Other than a slightly earlier booking opportunity for your first ride, it also treats on property guests and off property guests equally. Finally it didn't let you reserve/plan out rides in advance, rather your selections were being made day of, based upon line times and availability. It was geared toward being able to choice to skip a line as it existed that day, not preplanning a time in the future when you could schedule a ride.
I always thought Genie+ was a fairer, more equitable system. But as someone who like planning trips, thinks spontaneity is just laziness, and who always stays on property, subjectively FP+ was a better system (not taking into account one was free and the other was paid.) It appears based upon the data WDW has that 1) more/better benefits for staying on property are needed and 2) people like pre-planning their ride times as opposed to the simple skip whatever line i can at the time model. So its not that the new system is a worse version of Genie+, its that WDW wants the new system to do different things.