I might argue that kids should get a double period for math, especially earlier in their school careers — one class to teach the fundamentals, another class to simply explore. The benefit being that critical thinking is enhanced in all academic areas and not just the obvious in mathematics.

My first real mathematical experience was in second grade. My teacher had some hoops on the floor, and was putting coloured shapes inside. Red shapes in one hoop, and triangles in another hoop. But then the problem arose: what to do with the red triangles? It was total magic when she dragged one hoop to overlap with another hoop and placed the red triangle in the overlap. Venn diagrams for six year olds.

And I still can't multiply six times eight! I have to work it out every time...

No offense intended, but if that still bothers you, it's time to learn it.

Either by accepting the offer you got with 5 (that is, memorizing the multiplication table - BTW, it is more fun to do this with 15x15 or 20x20 rather than 10x10).

Or by playing mental calculation games and trying to get high scores in speed.

(Essentially, this is the same as with learning vocabularies for a foreign language. The word "4x3" is translated to the other word "12".)

Maybe your teachers failed to make it interesting to your 5-year-old self. But your current self does seem to be interested, so that can't be the issue anymore.

You can critize your teachers that they didn't make your learn it at 5, but you can't critize them for still not having it learned later as an adult.

Because there aren't any. The prime numbers would be gaps if you pivoted the table into a division table but, alas, that's not how it's presented (even in the context of teaching division.)