Yes, there are some subreddits about ideas, but they're all horribly hard to browse (and also full of garbage).

Key differentiators: - submissions are well-categorised (and there are filters on the repository page) to find ideas - submissions are moderated for quality and seriousness - recommendation algorithm is far less time sensitive than reddit (which basically stops showing your post after day 2). - a bunch of other useful features specific to ideas (eg: get notified when it gets executed – more in the making).

I'd say Oasis of Ideas can do everything a subreddit can do, and more.