The marketing ARG for KH4 is getting wild

If your backgrounds and scenery look exactly like your interactables (or they otherwise blend too well together), then there's no way to tell the difference aside from painting it. Otherwise you just let the players fumble around for hours trying to find the path forward.

I think the problem stems from the fact that most games that need/use it are ones without much of a visual style outside of hyper realism. If there were any ways to otherwise stylistically imply something is interactive, this wouldn't be such a prominent design motif.