everyone pays for the lightning lane. I've tried it without it, but the park is unmanageable. However, with the current system, you can at least reserve your rides at specific times which keeps the lightning lane moving pretty good, while standby can grind to a halt (especially around lunch time).
This new idea gets rid of the time reservation, which was specifically there to control the lightning lane size. So now everyone who pays the $400/person gets a HUGE advantage. So most people will adapt and just build in the $400 into the cost of their Disney Tickets like they do with Lightning Lanes right now.
Once you get a large percentage paying the extra $400 (good for shareholders) the advantage of the lightning lane vanishes as it becomes just another standby line.
Customer experience drops.