This design is kind of a polar opposite of the previous ones in terms of explaining what Mastodon is...

I think now there is much less need for justifying Mastodon's existence on that page, plus the original reason was that the page predated the existence of joinmastodon.org, so there was nowhere else to explain what it is.

Still, I think at least one short tagline should be there. Not sure where. Maybe right under logo.