This tutorial is fantastic! You're absolutely right that a common beginner mistake is trying to draw things as they see them in real life, just as complex and full of detail. But stylized art isn't about capturing all the complexities of the real world.
In stylized art we often use what's called "shorthands". A shorthand is a way of representing something with less detail and complexity, but still getting the idea across. The fur in this tutorial is a great example of that. A stickman is another popular shorthand for a human being. But it's just a few lines, obviously it doesn't look like a real world human being. Yet people get it. Our brains are great at recognizing patterns and filling in the missing details.
The best way to get better at this is to study other artists. If you're trying to draw a wall made of stone, look up how different artists do the same and really study their technique. What shorthands are they using to suggest the wall is made of stone. Where do they choose to add detail and where to they purposely leave it out. What shape language do they use.