It is a serious decline - Apple was literally the best there was at this in the past.
I noticed their design attitudes towards affordances and contextual clues changing around the time Ives made some claim about how phone users have been educated about touch UI sufficiently to start dropping them. That seems to have become an general excuse to lean towards 'pretty' over 'functional'.
And worse are third party apps. They always have been more variable, of course, but the old HCI guidelines were actually really good, so much so that people followed them because they were convincing.
UI decay isn't the only reason I use my phone and Ipad less, but it is one of them. (Current Screen Time: 24 minutes a day. That's mostly checking email while standing in line and mashing 2FA buttons.) The dynamic lists of recent activities and such mean I have to stare for a while to see what the options are this time, and generally be careful not to make mistakes. I've turned off autocorrect, because it makes enough enough mistakes that it is slower (and really irritating) to use.
I like my laptop a lot more these days.