Editing is everything. Cut until you can cut no more. What is left often springs into life.
“Kill your darlings” isn’t always referring to characters. It’s easy to want to hang onto every word you’ve written, but revision is one of the most important parts of the process. Without revision, you only have a rough draft. Drafts, no matter how good they seem at first, always need to be polished. Clean them up like they’re going out on a date with a publisher.
You can be the best writer in the world, and you’re still going to need to revise your work. It’s not easy, and it’s not usually very fun, but it’s a necessity. If you can’t revise, you likely can’t get published (speaking from experience here, haha).