Let's say I'm making a banking app that is generally just used for people to check their balance and other simple tasks. It's too my advantage to follow the standard UI conventions of the OS.
If, however, I'm making an app that I expect the majority use case to be power users that use the app many times per day, I'm going to optimize for them. That may mean seemingly unintuitive gestures, shaking the phone to switch between app modes, radial menus, or something else.
I'm not saying that conventions don't have a place, they obviously do, but I think app designers should be able to design the experience for users that they see as best, rather than following convention for the sake of convention.
Another bit of anecdata is the Android ebay app. It used to be an OK not-really-material app, probably iterated on since the Gingerbread days, then Holoiefied. Then about a year ago they updated it to be (I think) more iPhone-like and the fans really hammered it in the Play store. Lots of "what the hell have you done, 1-star" type reviews. I didn't like it much either. The problem was again that navigation was weird and non-standard. Everything was light-grey on white too, which didn't help. Then they updated it again fairly recently to be what you might call a prototypical Android Material-design app, and it really was a relief to see. Now it works great, there are far fewer weird mystery navigation parts and the reviews are picking up.
I get what you mean, that apps can add things outside the norm, but they really need to get the base layout right. If you have a few odd/power features, that's great, but don't make the whole app some weird Homer's Car-style monstrosity.
I hear this from time to time. As someone who has spent significant time on a number of platforms Windows and it's ecosystem, from 2000 until 8 at least, has seemed a whole lot more consistent.
Super-annoying things on Mac include:
* modifier keys vary by application. (On Windows ctrl + left/right arrow is always [0] jump word by word and shift + left/right arrow is always select-as-you-move. From there it follows that ctrl+shift+left/right arrow is select-one-word-at-a-time.)
* there is one menu and you can find most options there. Bonus: you can always reach the menu using alt. On Mac there is the global menu, helpfully located on another part of the screen or even on another screen and there is one or more spot-the-extra menu(s) somewhere in the application.
The reason why I am pointing this out is to help every developet who doesn't get MBPs thrown after them: Macs are super sleek but I at least feel more productive and less annoyed on Windows or Linux.
[0]: with a few super-annoying exceptions.
But the web does have conventions that make stuff hard when broken. For example most people expect to see the whole page change when they click a link and doing something else is confusing (such as popping a window or opening a link in new tab by default)
There is no shortage of complaints about websites that do "innovative" stuff and liberties with good ol' conventions.
Trying to build a native-osx or native-windows UI on the web gives you a horrible user experience.