[nas]

I suspect Tim's meaning was that ordinary users don't need to know how metaclasses work in detail. It is enough that people know they exist (i.e. do something at time class is defined). If you need them, you are doing deep enough magic that you can take the time to learn how they work.

Maybe he was also suggesting that people should generally not be using them. In my experience, it is exceedingly rare to need them. In 29 years of writing Python code, I think I've used them once or twice.