They're often too obstructive for no reason (often has a too large dark gradient that blocks bottom or top of the video), takes forever to disappear, and hard to operate (very easy to accidentally pause the video). For example, CC button for YouTube: it totally could be below the video element.
This is especially annoying on mobile since there is not keyboard shortcuts.
Youtube: missing on right arrow key and pressing numpad zero instead rewinds you to the start of a video. That’s truly idiotic, because no idea where I was watching.
Focus can be on a video, or on “controls”. You press up arrow to volume up, but it jumps +5s because focus was left on a seek bar last time.
iPhone: inputs zoom on focus-in but do not unzoom after you’re “Done”. Pinch the site back to 100% yourself, that’s so much fun isn’t it.
MS Windows scrollbars and their small reset distance.
General: Buttons that look like labels. Frames that look like air.
Vertical centering of bullet points next to multiline text.
Why the hell can't I start typing as soon as I get to that page?!
You really insist I use the mouse?! My fingers were just on the keyboard typing the url. Goddamn you
^^^^ I feel this way often. This is a solved problem for the past 20 years. As for the past 10 years, the same problem on the phone: Start at that field and bring up the keyboard
I live in an area with poor cellular coverage. SMSs can take as long as weeks (6 weeks in one extreme case) to get to me.