I've run into the same conversation a lot lately--with crit partners, friends, on Twitter... It has to do with revisions, and why they're important, and what they really MEAN.
Okay. This is an insanely common scenario when critiquing a beginning writer. (Note: "Beginning writer" = Someone who has not been seriously writing for publication. It doesn't mean you have to actually be new to writing itself. In fact, some of the most stubborn "beginning writers" have been writing their entire life. I know. I was one of them once upon a time.) They keep getting feedback like:
"There are too many characters in the beginning. I can't keep them all straight."
"This setting just doesn't feel authentic. I think you might want to do some thorough research."
"I'm not sure you should tell this story from an adult point of view. It doesn't feel like a teen story."
"I know you've worked really hard on this world building, but it's really dense and slows down the story."
"I'm not connecting with this character. He seems to just be an observer and isn't really contributing to the action."
"The writing here is good, but I'm not sure you want her to meet the mysterious Vampie boy in biology class because it's kind of overdone. Also, while I understand you're going for this half-vampire, half-kelpie thing, that name sounds...uh...stupid."
And this is the writer's response:
"Oh. I see what you're saying, but it has to be that way because of X reason."
"Well, it will all make sense later if you just keep reading."
"Yeah, but if I do that, then I can't do THIS later, and that is an INTEGRAL part of the plot."
Sometimes revising isn't really about just making what you have better. It's about letting GO of what you have. You don't ever have to listen to every suggestion (in fact, you shouldn't--that's another problem altogether), but if you kinda sorta understand what the person critiquing you is saying, yet you're resisting because "that would just be too hard" or "that's not how it goes" or "I don't know how to do that"?
If something in your gut says the story probably would be better if you could only find a way to do that, then find a way. Step outside the box of what you've already written. Allow yourself that freedom. Even if you've been thinking of this story for 15 years. Trust me on this. I've been there. When you write for yourself, you can write about anything your heart desires, but when you're writing for publication, what you're learning to do is no longer purely selfish.
What you're really doing, when revising, is learning to help a reader connect with the heart of the story. It is not so much about you anymore. The details and plot twists and characters you've so carefully planned are WORTHLESS, from a publication point of view, if none of your critique partners or friends can get into the story and no agent or editor seems to want to read it. If you insist on clinging to all your ideas, you will probably not get published.
The fact is, the details are not what make people love books. People don't love Harry Potter because the kids have to carry wands and speak Latin words to do spells, or because the Weasley family consists of this many members, or because it's told in Harry's POV. What grabs people is the heart of the story and the depth of the world and the excitement of the plot. You want to hone that, so you can change any specific part of the story that isn't working without losing the heart. Sometimes, change it drastically.
And trust me, it's no good to think, "Well, I'm just going to try and sell it anyway and see what happens." Because if an editor DOES buy it, it's quite possible they will suddenly want changes--HUGE changes. You don't have to agree, but you'll want a good reason as to why you're not taking the suggestion. Sometimes it's not even your editor who wants the change, but marketing--or even a chain bookstore! I know people who have made changes because the Barnes and Noble buyer wouldn't carry the book without them. You will want to be a flexible writer who can roll with that sort of thing. Otherwise your editor will be frustrated working with you, and you'll have to find some way of working it out because they will already have paid you an advance.
These are skills you should learn before you even try to sell anything. Your work will be much better for it!
I actually have another point I want to make that is kind of related to this topic, but this is already long, so I'll save that for later.