What you want to create is not something Discourse is aimed for.
You want a Reddit/Discord platform, where people can come and create subreddits/servers they “own” while your retain all control and monetization of the platform.
Discourse aims to be the complete opposite, allowing each subreddit/server/guild to be their own site, own their data and live in their own URL.
While you can hack an open source project a lot, I would recommend using something else that is closer to what you want.