There is no such thing as any potential trope being too common to make an actual trope.
Plots, Characters, and Conflict are tropes, and literally no proper story can be told without them (whatever form they take). That means that, by necessity, they have 100% use on any work that tells a story. If those aren't too common, then no other trope can be too common.
This is why Seen It a Million Times doesn't mean we can't trope it, and never did. It only means it's really common, and that there are perhaps too many examples to make listing them worthwhile. This also means that Truth in Television doesn't invalidate a trope (especially since it lists valid tropes on that page), because if there are reasons it's done in fiction (whether or not the reason applies in Real Life), then there are still reasons it's done in fiction.
Occasionally, a trope is so common, either throughout storytelling or within a genre or medium, that straight examples greatly outnumber aversions and various ways of Playing with a Trope. We can still list the latter instead.
Finally, People Sit on Chairs should not be used just because a trope is common. That's about lack of purpose, not too high a frequency. Something could be rare and still have no purpose.
Contrast Too Rare to Trope and Not a Trope.
