I decided to install the new version of iOS with this 'liquid glass' jazz. Apple gave its design rationale as getting out of the way of 'your content.' In a WWDC video an Apple designer breaks down how complex and subtle the transition animations are when floating controls shift from light mode to dark mode, to blend in with 'content' as I scroll.
I can see how someone could talk themselves into thinking this is a good idea. In practice, though, scrolling high contrast images can make the fixed-position controls shimmer as various blend transitions trigger and the controls try to keep up. This triggers those hunter-seeing-prey instincts and does the opposite of getting out of the way of (ugh) 'my content.'