Meanwhile I learned about SQL, statistics, product development, industry best practices, algorithms both optimal existing ones and designing new ones, data structures both how to make one and what makes good ones, and how operating systems are designed and function. Specifically, I wasn't just shown a vague example in a twenty minute youtube video, I was made to demonstrate my knowledge in projects and tests that were designed by an intelligent domain expert and educator to separate the wheat from the chaff and often did just that.

I use most of that every single day, and I'm basically a web app developer. Can you learn how to program from learning yourself? Sure. Einstein taught himself calculus, but that doesn't mean most people can adequately teach themselves difficult subjects.

Writing a for loop might not be a difficult subject, but understanding what makes a for loop slower than another method, or why maybe you don't need to loop at all if you engineer things differently is an entirely different thing.