You want to tell your story. You feel it: populate it with characters. However, to all that raw material into a novel is not just putting it into words on a page. You have to ensure that readers can relate to.
That is what structure does. If you ignore it you risk frustrating, or worse losing, your readers.
Some years ago, a writing teacher claimed to their class that there was no such thing as structure. He went on and on about this. However, if you looked at his materials and the terms he had used to designate various story beats unfolded to form a perfect traditional three-act structure.
When it comes to writing, fiction writers tend to fall into two camps: those who prefer to outline before they write, and those who find outlines too constricting.
The pillars of structure are equally useful tools for both styles of writing. If you like to outline, you can learn to set up a strong story by mapping out a few key structural scenes from the start.If you prefer to proceed without this restriction, you can continue to be as free as you like with your first draft. Understand, however, that later you will have to think about the structure of what you have written. This is because manuscripts that ignore structure are almost always filed under unsold.
Authors who purposely play with structure usually know exactly why they are doing this. They accept, as a consequence, that their books might not be as popular with the reading public as novels that have structure. At the very least, every author should understand structure fully before playing around with it.