Does humanity care about letting aliens know we once lived here long after we are gone? I doubt it. Without that political will, this expensive space graffiti will never happen.
Does "humanity"? I don't know. There's no way to know that without a poll.
Personally, I do. I think it's a worthy project. It would have been really nice if people in other ancient civilizations (Rome, Hittite Empire, etc.) had left us complete and detailed historical records safely locked away so that we could understand their civilizations and lives instead of trying to piece together a fragmented understanding from various ruins and relics that we've managed to dig up.
Is there political will? Obviously not. If there were, there'd be political will to fix our problems, but that doesn't exist either, so we're doomed to destruction of our civilization.
And a well-protected (and probably hidden, to keep random meteor impacts from wiping it out) cache of archives hardly amounts to "graffiti".
