I love Obsidian and the sync is worth it, but I wouldn't say it's one step above a text file. It's miles away. Never-ending features and customisations. If you want simplicity, a text file really can't be beaten.
The point is, you don't need to play with extra features and customizations if you don't want to, so you can keep it "a step above a text file". That said, having those additional features is nice when you want just a little bit more, or you want to link a note file with your todo file, etc.
I use Obsidian as basically just a markdown editor that I can throw images into. I find that all of the bells and whistles stay out of your way if you don't want them.