If you understand the difference between greedy algorithms and non-greedy, you also understand the difference between learning by doing and building a solid foundation before tackling a problem.

For most simple problems, it's true that the taking the seemingly shortest path to solving the problem is good enough. There are other problems where you simply have to understand the abstractions at a deeper level than you can visualize in code. It's there that things like reading a textbook or taking a course can help.

Can you give an example?

I mean: if you're learning a new language/library/framework it's really useful to have a broad idea of what the tooling for it looks like.. what features does it offer? You can look up the details when you need to

It's really useful to have a broad knowledge of algorithms and what problems they're applicable to. Look up the details later

If you're going into a new domain.. know the broad, high level pieces of it. You don't need to pre-learn the specifics of websockets but if you don't even know they exist or what they're useful for in web development.. that's kind of a problem

Even more abstract concepts like how to design code there's a lot of good info out there

If every generation had to re-invent the wheel from scratch we'd never get anywhere. The problem people have is they think ONLY reading is enough