"It's a romantic comedy about this woman and this man..."
"It's a thriller about a lobbyist who..."
"It's a zombie coming-of-age story..."
All loglines should have several things: a conflict, a main character and a genre.
Most screenwriting book will tell you the importance of creating a three-dimensional character and of having a central conflict with high-stakes, and unifying theme as well... They will, however, spend less time focusing on the genre of your story. Here's why you should explore the genre of your story.
Know your classics
Each story fits within the rules of a given genre, some of them better than others. You can dismiss that fact, and try to do your thing, and by all means you should do your thing, as no one else can do it, and the more distinctive your voice the better.
However, when you're writing "Fade in", or walking onto the set and drafting your Oscars speech in the back of your mind, you should also keep in mind the fact you need to abide by certain rules. Use them and break them if you wish to. But know them.
Knowing the classics of your chosen genre(s) will make you see the patterns of what works and what doesn't, and help you ascertain what you should do. Not only can it help unlock certain situations, it can also enhance your film vocabulary.
Thinking of what's out there when you're creating is not (necessarily) pandering or corrupting your vision. If you're not thinking about it, your producer or distributor or someone who pulls the strings is already thinking about it. So make the most of it.
By knowing what's out there, you can then channel that into subverting expectations. Think of Seven. It's technically a whodunnit, but as anyone who's ever seen it can attest, that doesn't even begin to cover what that film is.
It's hard out there
Finally, some genres have a very strong following: horror for instance. But then again, people turning on Netflix will think "I want to watch a comedy" or looking at what's in the cinemas "I want a good thriller". Genre will help define your product. Your work doesn't have to be the lowest common denominator -Hollywood has gladly unburdened you of that task, dear indie filmmaker. However, it will help put it in a box. Even if it's just one of many boxes by which your work is defined.
A genre will follow certain storylines, certain archetypes of characters that you can and should transcend. But you can create your own niche by doing your thing within a genre. With steady dedication, some people have become a genre of their own. "Woody Allen" is a genre, as is "Wes Anderson" and as are "the Coen Brothers".
Question is -what's your voice?
If you want to know where you're going, why not attend the Movie Genre Foundation Certificate?