some very specific questions wont show up on other forums that reddit has, since most people from other forums/sites moved to reddit to start communities there, or niche content. outside of something like health related fourms, are still healthy, or something about evading SOCIAL media bot/spam detection methods.
i was used to be on other forums that largely died out or became less useful because reddit had most if not all the answers or discussions. remember the subreddit bans in the 2017ish-2018, i joined a international forum that they migrated to and left that one, as it started to deviate from the actual original subreddit it came from. it did replicate the UI of old reddit quite nicely though.