Liquid Glass is the obvious regression in the room for me.

Windows 11. The "EOL" of Windows 10 could also be considered a UX choice.

I also recently upgraded from an iPhone 13 mini to a 17, and I'm still not used to the larger screen size. Phones that can fit comfortably in your hand and pockets are in short supply.

AI-"enhanced" Autocorrect can be a nightmare, especially when you're talking about niche topics, or different languages.

Infinite scroll and addiction-as-product-design is a scourge on many.

Previously non-algorithmic news sources that now algorithmically feed you headlines.

Lots of websites have a slightly-but-noticeably degraded experience on Firefox.

The Internet at large without uBlock Origin.

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Most of these are not design "choices" though, they are profit motivated. Good and/or humanist design often tends to be at odds with profit these days because attention is currently primary vector of exploitation for companies.

"More Usage" != "Good Design", but people do like to be employed and receive a paycheck, myself included.