Wait, there has to be an ironclad line?
I guess we can't use terms like "high budget" and "low budget" when talking about games, either, since there's no official line between the two.
And I suppose we can't use the name "roguelike" to specify a genre, since
nobody can quite agree on precisely what the term means quantifiably.
...or maybe some things exist on a continuum, not as stark binary contrasts. "Conservative" and "Liberal", to add some insight from the other side of GAF, have
slightly epically different meanings depending on where you are in the world, because the midpoint between the two is subjective. Just because they're not mathematically rigorous in their classification does not magically make descriptives useless.