Your observation about gaps in knowledge is true for all trades, and is at least conceptually what separates trades or job skills training university education.

A good university program teaches very few hard skills, but you learn to reason about your field essentially from first principles. On the other hand, to do a mechanical job, you really need just the job skills, and the connection to cause and effect is almost irrelevant.

This is typically why university education is held up as a better key to long term career prospects, because of the adaptability rather than rote memorization.

In real life I realize it's a lot more messy.