My perspective is that people who are just starting out sometimes become so wedded to a certain approach that they aren't open to suggestions that can make the project better.
I definitely understand the importance of telling the story that you want to tell, but the risk (in my opinion) is that you can make a movie that you love but no one else understands/likes/appreciates. Certainly not everyone needs to like your movie (believe me, I've had polarized reactions to my first feature). But it's useful to understand how and why that might happen, rather than to proceed with blinders because of what you love.
I think the biggest challenge is to accept that you are not good enough. You lack a big amount of "rules" which lead to a succesful screenplay. Unfortunately your unaware of this lack doesn't prevent you to attache your incomplete story to youself and therefore feel that this is you, this is how you write, this is your unique way to tell stories. The challenge is to realise that this is bullshit, that's not who you are, you are just an incomplete screenwriter and so you have to study hard to become able to write stories the proper way, the way that people tell succesful stories for thousands of years.
Creating an entirely new story is one of the challenges of being a screenwriter. You have to look to the story from a new perspective because you're going to compete with more than a century of archives of film. It'll be a frustrating journey especially if you aim to be unique. You'll hear a lot of people say that they already know what kind of twist or they know a movie like that already exists.