That's an extremely broad question. Are you asking specifically about email replacements, communication standards, or just proprietary software in general?

When has ever a “tech industry’s ‘reenvisioning’ of a free/cheap older, but universal, standard” resulted in “an open and free standard” and not “the usual bullshit vendor lock in”?

Never that I can think of, which is why I stated my hope that it wouldn't be like that. But maybe that just means we can't necessarily depend on a profit motivated corporation to do the 'reenvisioning'

Bingo. See also the rumored “definition of insanity”; i.e. doing the same thing over and over again, but expecting a different result.

Basically anything? When was the last time something like email happened? And it wasn't a giant tech company that created that either.

Maybe something like Webrtc?