Tropes can become discredited in a number of ways. Usually this involves overuse or changes in social values. But sometimes it doesn't even take that. When a Trope which may have been perfectly ordinary on its own is used so famously by one particular show, its meaning gets changed. Instead of what the Trope had meant before, it now means "Homage or parody of the show which used it famously." (Or, if you're less lucky, "Blatant rip-off of the show which used it famously.") Think of it as a kind of Real Life Flanderization of a Trope. See also Older Than They Think.