To truly face the fact that you will only ever be able to learn a tiny fraction of any given field is pretty depressing.

First, if that reality depresses you, you need an attitude adjustment. I got a PhD in EE which taught me that neither I nor anyone else knows squat. That's just the way reality is.

Second, the graph isn't enough without identifying levels of competency against some standard, which could be population statistics, or grade level. That's what's needed for education - realistic goals, and a way to track progress toward completing them.

That should be sufficient for schooling. After that, experts could recommend material based on desired specialties.