For me, it is the shift toward thin, auto-hiding scroll bars. I see it on macOS, Linux (Mint), mobile phones and probably Windows too (though i haven't used windows in a while).

Is this a cleaner look? I have always loved visible scroll bars because they act as useful guides for where I am on a page and how much content remains and just easy to drag. Now you have to hover over it first.

I am curious what UX changes have stood out to you lately, for better or worse.. Maybe some designers reading this forum will take notes.