I used to use an extension called papier that had a simple interface, just the right amount of configurability and a beautiful design (particularly good color schemes). The extension got removed because of its incompatibility with the new manifest V3.
The current alternatives are either too involved with too much configuration options (i.e. distractions) and not very attractive, minimalist designs.
With your app, you're almost there. If you can get the correct balance right, you could fill the gap in that niche.