You certainly don’t need - I know and have worked with many successful people who don’t have any sort of meaningful (beyond grocery list type) notes or externally-stored knowledge of any kind.

This feels like a comment without substance and in a way, it is. But I think it’s important to push back on this idea that if you aren’t managing a Second Brain while you’re GTD’ing a side project and Tools for Thought-ing your way through the western canon you’re wasting your life.