All of those things are still in use, although perhaps not as much as before. I suggest to continue to use it.
(Do you know my first post on Usenet (using a NNTP client program I wrote myself, actually) was in 2019? I still use it, although there aren't a lot of messages on there, but there still are some.)
I suggest if you wanted to make up a web forum or mailing list, to set up a NNTP instead please. I also invented Unusenet which is a way to form newsgroup names which are not part of Usenet (you can have both on the same server; the names never interfere). You could also have multiple interfaces to the same messages if wanted, making more use better.
With other protocols too (such as IRC), a bridge can be done. For many kind of text-basedinteractive uses, telnet (or SSH) is much better than using a web page.
And companies started dropping that when it became very important to their business model that they maximize the amount of data they can collect about a user. 3rd party clients for my service? Unacceptable, can't spy on the user as much there, and can't advertise at them. Communicating with users on other services? Unacceptable, I need those users on my service so I can spy on them too, and besides those other services won't talk to mine for the same reasons.
Don't know why you're being downvoted when this is exactly the case in my experience. They never said "spying" outright but it's definitely why walled gardens like AOL popped up like wildfire in the 90s and why stuff like AIM was the exception and not the rule.
AOL was not about spying on you, it was about collecting that sweet monthly fee.
And anyone who lauds Apple for bringing tech to the masses should consider that AOL did the exact same thing for the Internet and really brought a glimpse of the Internet (not just the web!) to the people. Yes, real techies might want to install their IRC client of choice and fine tune settings and all that, but Grandma just wanted to click on Chat from her home screen, go to the "Recipes Room" and talk about cookies.
It was the same "less choice/more consistency" of technology that let Apple get so big, with the same huge mass appeal (but with less panache).
AOL was more 'spatial' vs. the netnerds obsession with everything has to be (ASCII)-text delivered by simple but sometimes obscure to the average user, means.
I sometimes think one could easily replicate large parts of that with
