It feels like Apple did all of this in reverse. They created a new UI system and effects that look like shit with any amount of fine detail, and now suddenly their design guide says "actually fine details are bad for the user". They didn't come up with a good design, they came up with a shader tech demo and had to make a design that works with that new constraint.

Yeah, rendering at smaller sizes is one thing, but icons being made uninterpretable by system provided shadows and highlighting seems like an unforced error.