On the other hand, too many cooks in the kitchen could take a strong story and propel it into a glob of gook.
All screenwriters know that rewriting is part of the job of crafting a great script. Rewriting, rewriting, rewriting is a mantra for screenwriters.
So where do all the different ideas for rewrites come from? Well, I like to call on my respected colleagues for notes. I may have a rough draft of a script and know it has some strong areas and I'm wondering what others will spark to. So I give it to them to read. They come back to me with their thoughts that really help me to hone in on what is working and what isn't.
Sure, everyone has heard of the horror stories of notes ruining a beautiful script. Maybe the studio loves a core idea but they want the execution to be more generic, more mass audience friendly. This is when notes can tear out the spine to a story and leave it a muddled mess.
So in the end, notes are your friend and your enemy. You can't live with them and you can't live without them. For yourself, you need to have a confidence and passion and clear focus of the story you want to tell and know how to cull the best notes from the bunch.
And on the other hand, if a studio has bought your script and they want certain notes addressed, you need to do it -- even if you don't agree. They have purchased the rights to your story and they can and will make it whether you like the final product or not. So unless you want to walk away and let them find another writer to work on their notes -- which is perfectly acceptable and often a choice they make in order to get a fresh perspective -- you will need to be able put your "dreams" for your story aside and try to to make it work for the buyers of your script.
In the end, it's always wise to get other people's opinions on your work. It's very easy to get anxious and want to get your script out there right away. You dream of the quick sale. But the odds will be much greater for success if you take your time, get notes, vet them, work them in, and give your story the attention it deserves.
You wouldn't release a film without showing it to others and getting their feedback, right? So treat your writing the same way -- get the notes and learn to love them. If handled right, they will only make you look better and an audience more satisfied!