@Christopher
Nope.
Fans do have a say. For an example, look at early screenings. How many a movie has been redone, or the 3rd act redone because of early screening viewers saying, It doesn't make sense, its bad, etc.
Look at Last Jedi and Rise of Skywalker, they poo poo'd Last Jedi and the stuido done an about face and done some generic hash job for #3.
I'm not talking about what you mentioned like Airline Pilots, in that example, a closer thing would be a director having a bench of fans overlooking what he is doing and yelling at him to change it. That doesn't happen.
What usually happens is that people are hired, scripts made, and its filmed, by as you said profesionals. Thats all fine and dandy. Then it is presented to the people, Early screenings for example, changes are made based on input, or not, then it is released. It either does good or not based on if people like it. Now if its a one off, o well, its made, move on. If its a part of the series, then studios will look at what was unpopular, and strive to make a better next movie.
Simple thing of, you need an audience to make Money$$.
Another example, Movie X based off of Book X is coming soon! Fans of the book are excited. A synopsis comes out of what the story is going to be and who is being cast. Now this is where the peoples input come in. The fans can be happy, there following the book, casting good people, etc. Or Fans can be mad, There not following the book, the cast is crap. The studio at this point can make changes based off of the Fans input, Now if said fan input is just a bunch of basement dwelling twitter users, then they don't care and move on. If its more mainstream of alot of fans are mad, then changes may be made. The ENTIRE Reason for a studio to make a movie based on some other thing like a book is that there is already and audience Built IN, so there risk is less because those people "Should" pay to see it. If the studio makes to many changes from the book, the fans of the books Are Not going to see it.
Case in point, Ghost is the Shell. Yay a live action being made! Boo it has a white actress lead, Mega Boo there not really following the manga/anime story, Super Mega Boo at the first Trailer, Movie bombs.