If anything, the fact that people are attaching themselves to a medium for the sole reason its "cool", "quirky" and want to avoid the "weird" (which makes up like over 80%, certainly more of the whole medium) is far more telling of the decline rather than simple audience metrics.
The people freaking out over this proves that Anime/Otaku culture has only superficially gone mainstream. If anything, the hatred against actual Otakus has risen, with more and more superficial "fans" growing by the numbers. If someone posted this 8-10 years ago, no would care.