In that case, yes, I think icons should be "iconic" when possible. At this point, the "most used" version of basically every app is unsurprisingly an app. The phone app is used more than landline phones (or dumb cell phones). The camera app is used more than dedicated cameras. Word processors are probably used more than paper and pen.

So you either use something "iconic", or every icon is just a small screenshot, or I guess you make something up that is meaningless.