I think the majority of people care about communication, but not about the technology used to facilitate that communication. They'll take whatever tech is available to them and is convenient. Today there are is a lot more communications tech than just email and most of it is more convenient than email for most people. I'd personally like to see a desktop (or other UI) that unifies different communications methods (email, RSS, LWN, forums, Facebook, Google+, Wave, IRC, XMPP, Skype, SIP, IAX2, mumble etc) rather than continuing communications balkanisation; I care about people I communicate with more than the protocols I use to communicate with them.
Geary itself is a pretty good replacement for the GMail UI. Not sure I agree with some of their technology choices though (in particular; storage in sqlite instead of Maildir).