I find top-down organizational systems like Johnny Decimal difficult to maintain over time. There is an overhead in having to think about which folder something belongs in. And a similar cost to recall.
My own Obsidian vault is bottom-up. I assume I'm going to be in a hurry, or too lazy to organize. Instead I try to write wiki style with lots of [[Links]] to reference people/places/things, and the structure emerges from those links. This is the only approach that has stuck for me.