I wasn't being that pedantic.
Your list didn't include federated systems like Mastadon or IRC. It didn't include open source systems like Zulip that you can host yourself.
I don't use one of the big email providers, so I do get bounces when an organization thinks my ISP is untrusted. But that's not "can't even send e-mails if private companies don't like your 'sender reputation'" only "can't send e-mails to some people". And those people decided to use that system in part because they want the email provider to filter out some of their email.
We are not in a world where "all Radio and TV channels, newspapers and billboards are owned by private corporations." Member-supported radio and TV, and college radio, are still things, as is community/public-access cable.
Further, how do you want to change it? Do you want a government station which is required to be open access so anyone can broadcast anything?
Universities and similar venues for public speaking have always had the right to choose who they invite to speak. This is what freedom of association means.
Also, they are not a "law unto themselves". There are limits on the types of speech they can prohibit - a public university is restricted by civil rights laws, as is a private/non-publicly funded school which allows public rental of a space.
How do you want to change it? Do you want them colleges to be forced to accept any speaker on any topic, whatsoever?
We see events like the Gathering of the Juggalos, with 20,000 people, and wonder what you mean by 'only the absolute richest people could hold an event of any scale on land they own themselves.'
And I already commented on your "As it's private land" in my "fantasy libertarian future where everything has been privatized" - as something we aren't close to doing.
Yes, I totally agree that privatization of public spaces is something I don't like, though I'll point out the oddity of how the privately-owned public space at Zuccotti Park was a better site for the Occupy Wall Street protest than a public park, because the latter had curfews.