Hi,
I think a large chunk of this is that you're looking too far ahead. You're not writing what you want to write or read as others have said, you're writing or trying to write what you think other people would want to read. That's always a mistake.
Is your work too dark or too light? Too happy or sad? Too fantastic or mundane? I don't know. You don't know either. And even all those other authors you're comparing yourself to don't know. Because there is no answer. There is no wrong and no right here. It's just your work. It is what it is. And if you try to model your work on what others have written, it won't even be your work. That's an almost certain path to failure.
So write your book however you want to. And consider my basic creed. "I write for me. I publish for others." In short you write it, then you give it to someone else (or several someones) who can tell you it's too dark, too light etc. Writing in the first instance should always be selfish. It should be completely about you. About what you want to write and read. Your story. It's like any artwork, it's about communicating what you want to say. It's not about communicating what you think other people want to hear.
Editing / beta reading etc is where you start the negotiations between what you want to say and what others want to read. And a good edit should always be a battle where you stick to the core of your vision as much as possible, but look for weaknesses through other's eyes.
Cheers, Greg.