Right. And, I think, real expertise in any subject is choc full of tacit knowledge. Even - and especially - in areas where we have good symbolic representations. (Like music, math, programming and languages.)

The problem with English is I don't actually know the rules. Something just feels "off" sometimes when someone makes grammatical mistakes.

I doubt I will ever gain this feeling (for lack of a better word) with another language. I mean how could I? Everything sounds weird and "off" when you're a beginner, right? For example: el bano, el agua, la naranja, la sillas. You're constantly suppressing warning signs flashing in your head.

For example, I remember being forced to memorize the multiplication tables. I doubt we do that in schools anymore. I feel like all that time could have been better spent learning something else.

I think this is a function of hours of practice. I remember the point when I started hearing the silent "h" in Spanish and also when I stopped understanding what native speakers were saying after 3 months because I'd progressed beyond the level where they felt they had to slow their speech down for me. Lots of plateaus in the learning curve.

Schools still teach multiplication tables to this day. They remain useful in a myriad of everyday situations.