Why should you bother expending all the effort and energy to create a world? Only a small fraction of what you create will be seen in your story. What does it matter that 300 years before the story takes place a group of people tried to stage a religious uprising and convert the world to dandelion worshippers? (All hail the mighty fluff! Stare in awe as it floats on the wind to propagate a new generation!)
Have you read the Lord of the Rings? Or a Song of Fire and Ice? Both feel rich and vibrant because the world around the story is fleshed out. It’s not just a prop for the characters to walk past or through. It’s almost a character in its own right! Now, I admit that both J.R.R. Tolkien and George R.R. Martin have a tendency to become distracted by their own worlds (sooooo much description), but they aren’t the only authors to have created complex worlds for their stories. Have you read Jennifer Roberson’s Cheysuli series? What about Lois McMaster Bujold’s Vorkosigan Saga? Or Mercedes Lacey’s Valdemar series? I could go on all day (Terry Pratchett’s Discworld, Patricia Briggs’ Mercedes Thompson, Kelley Armstrong’s Women of the Otherworld series, etc.), but I think you get the point.
While some of those other authors may not be publicly known for their massive world building efforts, you can see it in their stories. The world isn’t just a bit of scenery or a prop. It’s affected by, and affects, the characters. This takes a good story and makes it captivating. This is why I’m such a big fan of world building.
And I’m not the only one. A quick Google turns up a world building reddit, questions to guide your world building efforts, numerous posts on how to build a world, even a TED talk on world building!
Depending on which tutorials you read, which videos you watch, or which guides you follow, you’re probably going to be getting conflicting information on how to world build, as well as what is and isn’t important.
This is fine (in theory) because there are so many different types of stories out there, and just as many worlds that need to be built. There really can’t be a single approach to world building that will work for everyone in every situation. I try to point out alternative methods in my tutorials, or at least acknowledge that there are different ways of approaching a task, but… well, nobody is perfect, and I’m no exception.
How much world building you need to do (and what types) is going to be entirely dependent on the story you’re trying to tell. If it’s a stand-alone short story then you probably don’t even need a full page of notes. Alternatively, a ten book saga is probably going to need fairly extensive notes just so you don’t say something in book 6 that directly contradicts something you said in book 2. (The exception obviously being if that particular something has changed between books 2 and 6, or if the discrepancy is deliberate and part of the story)
I’m like 99% sure I’ve mentioned this before, but I’ll say it again. World building is a very personal experience. Only you can decide how much you need to do, and what you need to focus on.
Just don’t neglect world building because you think you don’t need it. You do. Even if it’s just a little bit.