A few thoughts.

First, many people back then did not have permanently-online systems. You loaded the new stuff, went off-line, read, answer maybe, and uploaded your answers.

That gave you some time for meaningful answers (and - if you went the flamewar route - be smarter about flaming. Some got an almost baroque way of hiding flames in meaningfully-sounding sentences, which was, at least, funny).

I loved the aspect of doing the filtering on my end - not by an admin who decided what or what not I was allowed to read based on their own political leanings. Everyone had a freedom of speech, and I had the freedom to listen.

Can kill files be implemented today? Sure they could - we already have a pre-filtering by the algorithm curating what we see - I get very few hobby horsing stuff in my feed, because that's just not what interests me. This is analogous to the olden days, where the group, and the entry barrier acted as a pre-filter.

In my part of the usenet, real names were considered 'good manners'. That changed how people talked to each others. Of course, no-one could check if you were really called Klaas Hinkelman - but xXxStoneFakker666xXx was promptly laughed away - or landed in the kill file. plonk.

Another aspect that I really liked - and kept until today, was quoting inline, picking out individual questions of what could be a long article, and going into detail, like this:

    > [question or observation about an aspect]

    [answer to said question or observation]

And there was no upvote / downvote system, no karma, nothing like that. This removed the incentive to be 'popular', it was enough to be interesting, or just 'more correct'. It was perfectly ok to share a link to your private homepage, or take information there. Because no-one 'owned' an usenet group, there was no walled garden.

It is my strong belief that what killed the internet was not the September that never ended™, but vote gamification.