I really want to be as optimistic as you are, but I can attest from personal experience, not about chemistry, but about math - not everyone can understand basic

I really want to be as optimistic as you are, but I can attest from personal experience, not about chemistry, but about math - not everyone can understand basic mathematics. I often tried helping friends and classmates, in one-on-one sessions, to understand basic (primary and/or high school) math. Sometimes, you just end giving up. This was after trying a number of different approaches, different learning techniques, different ways of understanding / visualising abstract concepts, etc. Not everyone can understand abstract concepts (or our teaching methods are too primitive).