First books rarely fail on the writing. They fail on the hundred small technical calls nobody warned the author about.
Some first-time authors assume publishing needs years of industry knowledge and connections, so they never start. Others assume uploading a Word file to KDP is publishing, and end up with a crooked interior, a cover that is unreadable at thumbnail size, the wrong categories and a book that does not compete at retail. Margins, bleed, EPUB structure, ISBNs, keyword slots and pricing logic: each is easy when you know it, and each can quietly sink a first book when you do not.
The answer is not to become a publishing expert before your first launch. It is to work with people who already are, who explain every choice and leave every decision that matters with you.