Wow, this is a real bummer. My wife and I love the Magical Express. Aside from 1 trip with my family as a kid back in 1986 (we stayed off-property, anyway), I've only traveled to WDW in the Magical Express era. I don't always love standing in line for the bus or getting up extra early for the departing bus back to the airport for our morning flight, but there's still something fun about the anticipation as you approach the Magical Express check-in after getting off the plane and watching the videos on the bus ride to the resort. Something tells me that waiting in line for a rental car won't be nearly as much of a fun memory - especially now that the demand for car rentals will increase.
I'm sure this is all about cutting costs (or, being generous, 99% about cutting costs and 1% about misinterpreting guest surveys during the pandemic when the desire to sit on a bus full of strangers is at an all-time low).