I absolutely knew the names of the people I interacted with and whose projects I used. I even went to conferences with some of them. When I worked on my first web portal for Ubuntu we had a total of about ~4 dependencies and all was vendored. I knew the person who packaged my Python libraries for Debian.
You might call it an inaccurate description of history but it is very much my experience.
I know every name on mysql devel team.
The only reason i subscribe that mail list is: i reported some bugs and need to follows the release.
Signal to noise ratio on those mailing list was high. I can't say the same for github or discord
That's one project. You did not know every name, or most names, in FOSS generally. Today as well - a project which uses GitHub still needs a mailing list, web forum, chat channel (Matrix/IRC/discord/Telegram/whatever) to discuss and coordinate, and that hasn't changed.
As for whether signal to noise ratio on mailing lists was high - that really depends on the list. I don't see that much noise on GitHub repositories, to be honest - it's not easy to post noise that many people will see, so there's not much motivation for it.