I am a long-time Unix user, hardly an iOS user at risk of feeling lost on Macs, and while I have immediately turned back on my scroll bars, I was delighted by "natural scrolling," and I love that "Duplicate" makes it more clear that my documents are being auto-saved, as they should be.
These things aren't "dumbing down," they're just changes from the way things used to be. Some are better, some are worse, and both of those are opinions. I think labeling them as "dumbing down" and sneering dismissively at people who use iOS is unseemly, speaking of opinions.
Just to take one example, scroll bars were turned optional with default off -- a simpler UX that's in favor of less visible user interactions for the sake of reducing user complexity is usually considered dumbing down.
Now, in Apple Land, far behind the Reality Distortion Field, they may refer to the reduction of user interaction options as 'beautification' -- but everyone else usually just calls it 'simplification', which is often (diminutively, perhaps) referred to as 'dumbing down'.
(in reply to "scrollbars only disappear without a mouse" , so what? That's still a reduction in user-visible information -- do touch users somehow not need to be told that an active view can be scrolled by anything other than visual gestures and cues? It's a nice pipe-dream, indicative design, but there isn't any design standard that suggests that may be or even could be the case.)
tl;dr : when a user loses visible indications, and loses possible interactions, it's not uncommon to phrase the state as being 'dumbed down'.
But seriously: What you call "dumbing down" I'd mostly rather call "making peoples' lives easier".