My primary gripe with operating systems and computing hardware (besides functionality issues) is usually that
form is failing to follow function.
iOS 7's primary failure was that in ditching skeuomorphism (which wasn't entirely the wrong idea), it went too far and lost visual metaphor, not to mention most of the delightfulness and genuine beauty) Visual metaphor is the link between form and function.
iOS 26 and macOS 26 fails because they prioritize the "liquid glass" idea such that function is forced to follow form, not the other way around. Hence there's a lot of hard-to-read text, hard-to-discern visual boundaries, and big ugly one-off compromises (like the Music.app controls in the Songs grid view placed on top of the grid itself, with some transparency).