IMO tiny ideas like this are mostly for fun and learning, they don't need to be unique. Build another take on a blog or a game or utility or whatever you like to do online, but put your own spin on it.
Speaking from personal experience: just seeing what unsolved needs you have yields a lot of ideas. I had coworkers who would go to email something confidential to someone and click the wrong auto-complete contact and then we had a full-blown crisis. I thought "is there a way to stop that without the user hating me?" and that's how I got the idea for https://jiminyclick.com