TLDR not all perspectives have optimal legibility, but if it's easy to change perspective to achieve optimal legibility, then it might be a good tradeoff if you get other value in return. And phones have gotten bigger, and this is a reset of default device expectation.
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As an app developer I (generally) like liquid glass, it injects some much needed fun and freshness into our devices. It's still rough around the edges and some of these points are very valid, especially around not overdoing it to show off and some text-on-text issues.
However I do think some of the issues raised are based on a different goals around legibility.
I think NNgroup wants all interfaces to be optimally legible at any given moment. I think Apple wants all interfaces to have access to legibility at any given moment, typically by moving the screen a bit.
These are legitimate differences of opinion. A physical metaphor might be that you have a paper with a glass paperweight atop it. If one were to judge a photo of your perspective looking at it as though it were a UI, they might comment that the paper is hard to read in places because of the paperweight.
But in reality, it takes half a second to move that paperweight aside to read the paper, and the paperweight serves another valuable purpose keeping the paper from moving. This is akin to other purposes UI elements serve. It's a balance and a tradeoff.
Just like Steve Jobs pointed out to Round Rects Are Everywhere! [0], the physical world is full of content that obscures other content. What do we do? We turn our head a bit, or move a thing aside. We don't expect the physical world to have optimal legibility at all possible perspectives. While we can (and should) do better in the digital realm, there is a spectrum and the optimal point may not be where NNgroup wants it, especially as the capability of mobile devices reaches and exceeds that of the physical realm.
To address another point this article makes about touch targets:
Prior iOS versions made decisions about spacing between icons that were based on smaller devices (4.7-5.5", or 9.5-13 sq in). iPhones are larger these days (6.1-6.9", or 14-18 sq in), so the physical area of a touch target isn't actually that different, if at all. A big UI refresh is the time to update these kinds of assumptions.
[0] https://www.folklore.org/Round_Rects_Are_Everywhere.html