"Trying to build a framework to understand frameworks" is not the same as "use you own frameworks on your professional projects"
I have written my own Forth, my own filesystem, my own Mvc etc. etc. and I would say they have improved my skill more than learning a new Algol derived language but I would never advocate their use in production.
For learning it's a good idea to make something from scratch, way better than writing todo apps :) It can even be better than the original one.
For productivity it's not the case however.
