This one caught me completely off guard when opening YouTube the first time on an iPad: Accidentally clicked on a wrong button and got stuck in a "please subscribe to premium" modal. No amount of swiping or tapping outside the popup would help, only thing left was killing the entire app.
This experience put a major dent in my perception of the "Apple has the most intuitive UI" narrative.
The YouTube app has non-standard and nonsensical UX on every platform. It's Google's fault, nothing to do with Apple.
Case in point: The YouTube app for Apple TV. Everything (pausing, playing, changing subtitles) has been done opposite to the standard player found in every other app. You cannot use the main button to pause and resume, for example. Recently they broke swiping. Normally, you swipe the remote to navigate between UI elements such as squares in a grid or in lists with a light touch. It's very fluid, like a touch screen. But the YT app has added severe "inertia" to touch gestures, and you now have to "fling" your finger on the remote trackpad to navigate. Everything feels syrupy and stuck.
YouTube and Amazon's Prime TV app are the two worst apps I've ever used on Apple TV. I believe they both use some non-native UI toolkit that doesn't respect native OS conventions and doesn't even try to. Pretty incredible given the size and budgets of these companies.
The YouTube app does the exact same thing on Android. I ran into this just yesterday on my gf's phone, as I'd just added her to my family plan, tried to verify the settings on her phone, and it trapped me on an upsell screen for YT Premium that I had to kill the app to get out of.
How is bad UX in the YouTube app Apple's fault? You can mess up Android's back button as well.
Because Apple does not enforce uniformity
If Ah, yes, problems with the UI on the OS which for 99% consists of modals is not the OS vendor problem, noted.