I started Free.ai as a weekend project with the same mindset. And a month in the work hasn't stopped. So I second this. Just find a good name, it helps.

This can be the mindset now with a lot of things.

If you want a certain app with a feature and the app isn't open source, then you may as well just clone the app and add the feature.

Claude Code and Codex (and other tools) have computer use and are perfectly capable of navigating, experimenting, cloning functionality, writing tests...

If the app is open source it's probably easier to just fork and add your features though. And cheaper.