> Exactly. Up to some point, you actually do well because you are smart.

No, you do well because you put in the effort. Even trivial effort is still effort. Sometimes it's all that's genuinely needed (quite often in fact!) and it's important to realize this - but not always, and that's important to realize as well.

> my kids didn't learn anything new during their first three years

I think it's almost always possible to revise even these 'trivial' subjects in more depth. Granted, it's hard to do this in elementary math without some kind of outside involvement - someone to explicitly introduce the nuances. Other subjects this is quite a bit easier.