A few months ago I moved from Bear.app to Obsidian, because I wanted:
1) folders, not tags 2) easy access to the underlying files 3) more flexible UI
Obsidian did all of those things, and also has amazing community plugins (like custom data queries!!) that reminds me of the early Firefox days , but the thing that I did not grok until this week is that being able to theme using CSS means any theme I apply on my computer also syncs to my phone? It's like a build-your-own-iOS app!
I only discovered this when I was trying to tweak Byword/Scrivener to do what I needed them to do, and thought "I wonder if I can just find an Obsidian plugin", and the answer is yes. Open source is miraculous.