I love Liquid Glass. I think a lot of the complaints are whiny and pedantic. I do agree a bit of tender love and care could be used to clean up some GUI elements, but people act like Liquid Glass fried their logic board and rendered their machine utterly unusable.
The problem is, on iOS it's buggy. Floating opaque rectangles blocking you from seeing what you're doing. Software keyboard not being accounted for in the layout so you can't click buttons. It looks different; sure, whatever. It's getting in the way of actually using it that raises ire.