Yeah. The Cities: Sylines pop up video add is kinda annoying.
The issue is that it auto-popups if you leave your mouse there for 3 seconds… but if your mouse is already there when the page is loading then you might get the popup before you even realise it. (Which is what just happened to me).
I didn’t have any issues with the close button being behind anything, so that might depend on screen resolution / browser / etc.
IMHO popup on mousover ads are 99% as annoying as popup ads. They’re clearly designed to be popped up accidentally, which makes them just as sneaky and annoying as ads that popup by themselves.
There’s also the fact that it then autoplays (and therefor downloads) a video, which is often enough to kill the page / browser performance if you happen to be on an older PC or have a lot of tabs open.