As I often say, I haven't been here long, but I notice a sort of political-esque conflict between empirical clusters of people that I privately refer to as the Nice People and the Forthright People. The Nice People think that being nice is pragmatic. The Forthright People think that too much niceness decreases the signal-to-noise ratio and also that there's a slippery slope towards vacuous niceness that no longer serves its former pragmatic functions. A lot of it has to do with personality. Not everyone fits neatly, and there are Moderate People, but many fit pretty well.

I also notice policy preferences among these groups. The Nice don't mind discussion of object-level things that people have been drawn towards as the result of purportedly rational thinking and deciding. The Forthright often prefer technical topics and more meta-level discussion of how to be rational, and many harken back to the Golden Age when LW was, as far as I can tell, basically a way to crowdsource hyperintelligent nerds (in the non-disparaging sense) to work past inadequate mainstream decision theories, and also to do cognitive-scientific philosophizing as opposed to the ceiling-gazing sort. The Nice think that new LW members should be welcomed with open arms and that this helps advance the Cause. The Forthright often profess that the Eternal September is long past and that new members that cannot tolerate their Forthrightness are only reducing the discussion quality further.

The current LW is a not-so-useful (certainly not useless, as far as I'm concerned) compromise between the two extremes. The Nice think that the Forthright are often rude and pedantic (often being from academia, as the Forthright are), and prefer not to post here. The Forthright think that the discussion quality has fallen too far, such that the content stream is too difficult to follow time-efficiently, and that to do so would have little value, and prefer not to post here.

I know that you specifically spoke out against subreddits, but I think subreddits would help. Last time I checked, the post was called Hold Off On Proposing Solutions, not Hold Off On Implementing Solutions Indefinitely. (Excuse my Forthrightness!) Tags are good for getting fed the right content, but subreddits encourage subcultures, and subcultures already exist on LW. If you posted in a more technical subreddit, you could expect more Forthright behavior, but also super-high discussion quality. Forthrightness really isn't so bad in a semi-academic context; it's the outside-LW norm. If you posted in a sub-reddit for object-level lifestyle stuff, or miscellaneous stuff, you could expect more Nice behavior; that's also the outside-LW norm. This might actually be a case of LW collectively overestimating how atypical it is, which is, so ironically, very typical.