Communities are defined by the content contributors first and for most. That's something Reddit forgot.
Reddit started with a little bit of modding to clean up the mess which is always needed (how it works on HN). Then every year it seemed to grow and grow, mods were now self-annoited editors of their own pet magazines. A hundred plus mods were added to major subs, where in some 50% of comments can get removed in major threads. r/science has many many threads where 75% of comments were removed, almost entirely as they didn't fit some idea of what should be discussed, what was acceptable.
That's a big difference from RTFM culture on forums.
You write about developments on major subs, but those are just that, the major subs. Niche hobby subs, on the other hand, often don't see the level of moderation they actually need in order to retain knowledgeable contributors. People with a certain level of proficiency in a hobby will bail if the discussion is predominantly newbie questions or repetitive arguments.
I actually don't like locking posts either; the concept is fine, but in execution it felt more like a band-aid for when a moderator was tired of moderating, often because of 1-2 specific chains of comment and everything else was perfectly civil. Rotten apple ruins the barrel, and the feeling of mod laziness means they throw out the apples and the barrel instead of pruning the fruit.
>You write about developments on major subs, but those are just that, the major subs.
which is what proportionately most people will experience. moderating 100 people and 10m people are different problem spaces, similar to sorting 100 items and 10m items. They need different solutions and approaches to perform them optimally even if the end result is the same.