I agree with your broader point but I'm always skeptical of the claim "we should teach xyz in schools!" Because, well, choose your least favourite subject at school. A language, history or geography, mathematics perhaps. How much do you remember? The reason you don't remember is because you weren't motivated to learn, since you didn't, at the time, think it worth learning. If you think kids are champing at the bit to learn systems thinking, or how to file taxes, or law or anything else really then you are unfortunately wrong.
And I agree with the commenter’s well-meaning, but we are technically teaching systems theory already in schools. If you’ve had classes in any of the natural sciences, you’ve had systems thinking. If you don’t remember a whit, well then, proves your point—it’s probably not that great of an idea afterall.
The question however is if students are ever challenged or encouraged to apply their learnings beyond the classroom and in daily life. In my experience, the answer is usually “no”.
To me classes being boring and forgettable has more to do with the method of teaching than the subject. Just about anything can be made interesting with the right approach, and often that approach isn’t the typical textbooks, tests, and rote memorization.
Perhaps I’m biased, though. I learn best when provided with working practical examples and hands-on exercises that allow me to develop my own internal models. They can make a concept “click” where I’d be beating my head against a wall with traditional methods for a much longer period of time to achieve the same revelation.