Brilliance doesn't come in the first draft. Brilliance is accumulated over drafts.
Writers are very lucky because we can take our first drafts and over time develop and craft them. A first draft is like Adam's rib. We add the muscle, nerves, flesh, hair, and breath of life. Editors, publishers, and fellow writers help us polish the work until it shines and communicates perfectly, and keep us from making public our inevitable misjudgements and mistakes. That's why your favorite writers dazzle you. How do they do it? Revision. That's why years pass between their books.
We all want to write brilliant first drafts and be done with it. That's like wanting to climb Everest right this minute without a base camp or a team, or have a baby right now without a pregnancy. That'd be brilliant, but it's unlikely. Don't pressure yourself with the belief that you can or should write brilliantly immediately and all by yourself all the time--that you must be superhuman. That will be unproductive. Revision is very human. The humanity which soaks into the work through revision is what makes it brilliant.