On: A realization of why email is critical infrastruct...

[riffic]

email, as ancient and flawed as it is, is a shining example of the Lindy effect in play - the future life expectancy of a technology or an idea is proportional to its current age.

https://en.wikipedia.org/wiki/Lindy_effect

Any replacement will have to keep the above in mind because there's no test like the test of time.