Listen. Every authors hits a stage in their book where they question everything, where they doubt themselves, where they want to give up. It happens because you are comparing a working draft to finished manuscripts again. Which is a bit like asking why apples on the tree don’t taste like apple pie. There’s a relation to them, but apple pie does not grow on trees.
Finished manuscripts don’t have a final form until the cook in the reader’s head. You cannot produce apple pie with apples alone. You can’t produce the polished books like what you read elsewhere to a draft of anything you write.
Your drafts will always and only ever be apples.
Some of the stories are still seeds. Some are blossoms ready for the pollination (the work you put into writing the first rough draft), some of them are ripening in edits. Some of them are ready to harvest to go to the story-packing plant to be polished by beta readers and editors. Some of them are ready to get shipped to the store. But none of them become apple pie until someone buys the apple, takes it home, and does the work of reading the book.
Don’t compare a still ripening apple to apple pie.
Don’t compare a manuscript in edits to a finished novel on the shelf.
They are not the same thing. And you’re hurting the end product by trying to rush the ripening process. Let it be. Let it grow. Let it develop naturally. Edit by edit. Line by line. This will get better and the book will get finished. Have some faith in yourself. First book for one hundred and first book, they all have a stage where you think they’re hopeless. They aren’t. They’re just growing. Be patient.