The abstract concepts are useful, but in practice most effort is spent on applying rote symbol manipulation rules to questions specifically designed such that a

The abstract concepts are useful, but in practice most effort is spent on applying rote symbol manipulation rules to questions specifically designed such that applying the most obvious rule at each step will reach the solution. The idea of a tree search in symbol manipulation is never taught, so if you try solving non-trivial real-world problems you will likely manipulate yourself into a dead end. Highschool calculus should be taught with computer algebra software. That's what you'll use in real life as soon as you find an even slightly difficult calculus problem. There's not enough time to teach both the symbol manipulation rules and the intuition.