Self-moderation doesn't work for any reasonably large community, if you don't want your community to be generic Facebook/Instagram quality posts. Community-based moderation inevitably makes any subreddit into "fun phots/videos" because people who browse largely don't care about where the post is, they might not even realize what subreddit it is in when up-voting.

Subreddits like askscience or askhistorians would be impossible without extremely strict moderation, for obvious reasons.