In Music Theory, one of the first things you learn to do is write music in the style of the common practice period. That's shorthand for writing like Bach.
While Bach will occasionally bend some rules, he more often does his most interesting work by using them against each other to come up with unexpected results rather than actually breaking them.
The point being, that there are well-defined mechanisms in music such that if you follow them to the letter, your music will sound like Bach--at least a really boring version of Bach. But still, you're starting with that as a baseline. And as you practice that style and get more familiar over time, you start to see opportunities for more interesting options than what the baseline rules seem to suggest.
And as you progress through a theory curriculum, you start studying other styles and sets of rules for other noteworthy composers. You spend some time imitating Haydn and Mozart, Beethoven, at least one of the Russian epics, 20th century and modern composers, and sometimes you might take the time to go back and learn the styles of pre-Bach composers.
By the end of this series of courses, you have a solid understanding of the rule-sets that different composers were drawing on and how they were using and abusing them.
You, yourself, might not be a particularly brilliant or inspired writer of music. But you have a minimum baseline ability to write something that could pass for any of a number of famous composers from the 16th century to the present day.
That won't make you rich or famous or successful or even good. Because there's a lot more to it than that--mostly luck. But you won't suck. At worst you'll be unoriginal and derivative. Then again, you can say that about a lot of contemporary composers and writers.
My point is that you can go through a course of study either on your own or at a university and just through simple practice, achieve a certain level of skill.
It completely baffles me that for as long as people have been writing and teaching people to write that no such formal system exists in that realm.
This particular collection of "rules" is not a bad example of all the gobbledy-gook that we get taught in writing classes. But it's all entirely subjective, and there are famous counterexamples to every single one of them.
It's . . . I don't know. It's just baffling to me how this situation exists.