If you aren't a Reddit user, how can you judge what is causing the death of Reddit? It's your personal anecdote of why you don't use Reddit, but clearly there is an enormous userbase that was using Reddit despite the low amount of global moderation.
As a longtime Reddit user, this post struck a real chord with me. Horrible crap on Reddit does exist, and sexist/racist/hateful/uncalled-for-jackassery comments seem to be more and more common in the defaults and other places where the mods don't keep REALLY tight control.
It is getting, slowly, worse. Not because of the number of people but the standards of behavior they keep pushing the line on without pushback.
I think the biker bar analogy is fantastic. Even when the bikers stay in their corner their large number is getting scarier and more creepy.
I've seen this in the European-focused subreddits lately. Places like /r/europe are usually pretty "normal" discussion boards considering that their demographics are English-speaking, internet-using young people of those regions. But periodically the comments (and comment scores) end up very uncharacteristic in a thread or sub-thread, especially if it has to do with immigration, Islam, or nationalism. Not just in the sense that some people have conservative or nativist views on those subjects, but that suddenly the discussion seems to be totally dominated by extreme versions of those views, anything vaguely liberal said about the subject is downvoted to infinity, etc. And the reason in that case if you dig around usually turns out to be that someone in a far-right/xenophobic subreddit linked there and caused an influx of people with those views.
I haven't noticed it getting worse; I have noticed people complaining about it more, though. The up-vote down-vote system turns everything into an echo chamber anyway, so whatever racist or objectionable comment you see will probably go away unless the majority agrees with it.