It’s the ritual. Any productivity system can be made to work once it becomes a habit and therefore your default action.
I think .txt files or Org mode are attractive to devs because they feel like something we’d be doing anyway during our day. the same system will work with a paper journal or even a fresh piece of paper every morning if, and only if, it can be integrated into your natural daily workflow as an automatic habit. I personally found that paper is better for me because I get to it before unlocking my computer and being confronted with work and communications and notifications that compete with it. However, I have a lot of peers who couldn’t hang on to a paper journal or TODO list during the day if they tried, so digital formats win.
The real key is to make it a habit and learn to stick with it.