Just slide the screen with a finger from top to bottom to close an application.
Such Jesus apps do depend on the developer not being lazy / retard. While MS checks apps during the winstore certification process, sometimes apps slip through that do not react to such events correctly. Using those apps is pretty annoying.
So I discovered the "sort of task list" you get by swiping rightward from the left and then back to the left. I tried then dragging the thumbnails up, down, left, right. Nothing.
I figured eventually I'd take the time to search for a how-to, but what I was doing was just a stream-of-consciousness.
So I guess I avoided it by not seeing it at all.
Once you know it--the close swipe--it seems obvious enough. But just randomly swiping this way and that, I didn't stumble upon the long-swipe-from-top, which is not to be confused with the short-swipe-from-top which opens the context menu at the bottom of the screen.