Well, I recommend you not to mind first what the audience thinks or feels. Sure, all of us want to have a story that actually entertains others. But if you let yourself be limited by the gaze of others when exploring other styles or scenarios, your comic is nothing but a truck fueled by fear. You always carry the burden whether your stories are even worth it or not.
I have 4 suggestions:
1) Explore all possible techniques of story-telling or painting so that you have multiple choices and drop what doesn't seem to work.
2) Have a few comic buddies who are willing to praise and critique your work AFTER you drew all of your chapters.
3) Aim for shorter stories than longer one. If the short story works well (i.e the readers loved it), probably your style "would" work on longer ones.
4) Don't aim for profit yet. Yeah, I know we want to be rich and it's not really bad if we have such goals or whatever. However if you let yourself be bounded by it, your exploration of comic creation methods and techniques would be limited and you might repeat the same old styles and mistakes. And that's what you don't want to happen. Just like the gazes of an audience paralyze you because of fear, so does the mindset of profit-making and money.
As for your concern in style.Yes.It doesn't fit on the norms. Most dark plots tend to use a mature style of drawing to indicate the depth and realism of the story. However, there are stories where cute designs are used in horror and thriller and sometimes really mature stuff. As I want to spell the name, they are too mature so I'll just give one that uses cuteness but has a violent plot. Made in Abyss.
Try to read the manga or even watch anime. It's so cute and adorable. But as the story goes, the abyss is not a safe world as we are led to believe. The misleading of cuteness is a perfect blend for the making of surprise and suspense. Yes, it has drama and mystery.
TL;DR:
In short, don't be discouraged. Artists such as yourself naturally go to such phases where they feel unsure of the art they make. Doubts and fear will lead you to the abyss if you keep staring at it. So, I suggest you get critique buddies and try many stuffs.