Thunderbird users? I'd say ~100% of them use imap, probably ~75% of them use calendaring. I don't know whether Thunderbird uses ical or imap-type calendars behind the scenes but it works with gmail, zimbra and apple type shared/hosted calendars which account for basically ~100% of the non-exchange type calendars in common use. It probably supports exchange-type calendars too though I've never tried that.
I'd wager less than ~2% of TB users use a non-slack non-discord non-irc chat.
I think that TLS is the only new protocol level feature I'm using compared to 30 years ago. Anything else is in the UI and keeping the software compatible with new versions of the OS.
What was I using back then? Some emacs mail client with filters I wrote in elisp. I got my current folder structure started in emacs (roughly one folder per person and customer) and kept it through all the moves to Eudora, Netscape's mail client and Exchange Express until I landed to Thunderbird (desktop) and K9 (phone, much later on.) Work email was on Exchange when I was an employee, always separated from personal email.
Which works so well across multiple devices, which is a very very common use-case for email. Either you have some homebrew sync going on or you have a very simple email use-case.
My 35 years experience with email: I don't need to read old messages when I'm not at my computer. I never did before 2011 (first Android phone) and nothing changed after then. I can easily figure jobs that need constant access to the complete email archive. Not my one.
And I don't need mail on tablets and my old phone. I've got my main phone always with me, but the setup would be the same.
One reason it works for me could be that communication moved increasingly from email to messaging platforms and those are on my phone, except Slack which is confined to work boundaries. However I feel like I can lose all of WhatsApp and Telegram messages with no harm. I already lost a few years of WhatsApp and nothing happened. Who cares about conversations of 3 years or 3 days ago. It's mostly nearly unsearchable trash. And everybody else and I never had a verbatim trace of any IRL conversations for million of years, so they could be nice to have feature but not an important one.
But I'm doing my best not to lose mail. The long term important messages are in there.
[citation needed]
Maybe Jabber has more? But I doubt it.
It does, if you opt in.
You can also disconnect from IRC entirely from the bridge admin room.
Finally, if someone joins a channel via Matrix and then disappears without parting or disconnecting, then after 30d we’ll boot them off IRC anyway.
[[Citation needed]]