> The latency is too high for truly real-time communication
If you want real-time communication you really ought to be using VOIP.
> There is no cryptographic verification of the sender's identity (this problem is also shared with telephony). This has lead to really harsh anti-spam measures that make it hard to self-host. Sender verification + client-side sender whitelists would solve spam for good. It also means grouping by sender gives a very false sense of security regarding identity continuity between messages
I agree that the crypto situation in email needs addressed. I don't think that the answer to this problem is "throw it away and start competing standard #1982374" though.
> There is no good support for groups or threads.
Mailing lists are groups. Threading actually works quite well with subject-line threading. Mailing lists have been doing this successfully for decades.
>Clients do not group by sender, group or thread,
Some do. Gmail does, for example.
>Partly for historical reasons (it's just mail on a computer!) and partly for technical reasons (there is no sender, etc.) email is presented as huge letter-like affairs, leading to a felt need for all sorts of formalisms for every single message even if the messages are two minutes apart. Also email signatures (with logos?!) being attached to every message are just so wasteful both in terms of storage and in terms of screen space
The formalisms thing isn't actually true, and all of these are social problems, not technical ones.
It's okay to just admit you don't like email, even if it's for purely subjective reasons.