So, no, just having a bunch of magic unlabeled buttons and saying "use the keyboard" isn't good usability. The part that kills me, is that a lot of these applications don't even really have shortcut key guides. So, you don't even know the magic key sequence for something until you discover it by accident.
Worse, are the crappy programs that break global key shortcuts by using them for their own purposes.. AKA firefox seems to manage this on a pretty regular basis. Want to switch tabs? ctrl-tab, oh wait, it doesn't work anymore, cross fingers and hope someone notices and fixes it (which they did).
Not even Windows itself has, any where that I could find, a list of all the keyboard shortcuts. I find multiple lists, each with a different random subset of whatever the actual set is.
Sometimes I'll hit wrong keys, and something interesting happens. I don't know what I did, so it's "oh well".
You try to get around it by using an editor that shows tabs or an editor that re-indents the code but plenty of editors (notepad, nano, vi, emacs) don't show tabs as different from spaces by default.
https://wiki.c2.com/?SyntacticallySignificantWhitespaceConsi...
I do feel that some modern changes are annoying and unnecessary though and the instances I see that increase as I get older. I just always try to check myself and analyze how much of that anguish is just from being used to something or not.
I will finally say the examples here of inconsistency between evince and MPV is just inexcusable. You can't both break expectations AND be inconsistent, it's like the worst of both worlds.