Can you find a security expert RECOMMENDING email? That would be a better example of how it's not a consensus, like you claim.
These people might not be crypto experts, but hopefully many of them are security experts.
Gpg is also how most mailing list communication is (clear-)signed - and that coupled with public archives does give a way to verify that the person that controls the key that signed release notes for this package these last five years, is the person that will be able to read this zero-rated report that is critical. (It says very little about said owners real identity, or his or her legal name)
What does FreeBSD, OpenBSD or Oracle recommend for sending sensitive information to security@<company|project>?
That said, modern email suck.
Mutt (possibly with "not much") might "suck less" - but we need many more, better (graphical) email clients. I think Fastmail's work on a json-based client protocol is interesting (not because it's json, but because every blank staring IMAP-client writing developer keep saying that there are terrible horrors laying in ambush for the unwary).
Opera had a nice, new-ish, fast mail client. Other than that I'm unaware of any serious effort to make a new, modern, easy to use IMAP client. Let alone an open source one. Or one that doesn't beg to expose library bugs by rendering html, images etc in-line - or ignore user privacy by loading external resources that enable user tracking.
I've been contemplating writing one for quite some time.
Oh, my, yes. Lasciate ogni speranza...
[0]Rename: https://medium.com/@RiotChat/lets-riot-f5b0aa99dc8e#.3toozs7...