I know that right now, you probably want to give up. You want to trash that manuscript, burn it with fire. It's not good enough and it never will be. And you're right...if you give up. Keep pressing on because one day, someone is going to look at your writing and say, "You should publish that." So, Younger Me, stay strong.
Keep pressing on. Keep writing. Keep revising. Keep polishing. Keep querying.
One day, it will all be worth it. Your writing will touch someone. Your writing will bring light to the darkness. Your writing will be good enough.