KDE

Same. I hate it on modern smartphones as well. And ads often use it. I've got a few ads with X hidden partially behind the rounded corner.

Not the best photo, but I obviously can't just take a screenshot of it. You still get the idea from it:

Yeah, I don't really comprehend how people can rationalise the gaps. I want my windows to be tessellating!

I like it for some things, like an application window, since then it's clear where the window ends

I don't like it for everything though, like the bar at the top/bottom