If you're going to write a fantasy book, I think you're going to have to read the genre. What you read ten, fifteen years (or however long) ago doesn't count as much, I don't think, because then you probably wasn't reading from a writer's standpoint.
For example, I'm writing a mystery novel (well, sort of) set in the Southern US. It's not a conventional mystery and can't be shoved into specific genres like cozy or police procedural and while there's not anything out there I think that is exactly like it, many of the themes are present in other books. I think my reading material inspired what type of work I wanted to write. In my free-time I read thrillers, horror, fantasy, Southern lit, mysteries and general fiction. I learn something new from each and every genre I read, but at the same time, you're not going to know what's out there and what's expected for the genre, if you don't read and study it. I wouldn't limit myself to the genre of the book you're writing, for many reasons, but I wouldn't expect to be able to write a successful Southern novel, without reading the genre from time to time. You can borrow ideas freely. I'm not talking about stealing plots or characters, but little tricks of the trade. Like dialogue, for example and word choice, among other things. See how these authors create fantastical elements, how they balance realism with the fantastical, how they create mood, plot, etc.
As you work out your novel, I'd suggest writing short stories in between, maybe set in the real world. While you may feel that the fantasy genre leaves you with many open windows, it's incredibly hard to get right and to write something original and fresh. Writing pieces set in the real world can help a writer get a grasp on how to create imagery for the reader, among other things. It'll help you develop a style that you can apply to fantasy Besides, most fantasy mirrors realism, if you get what I'm trying to say, I'm having a hard time trying to say what I mean. While there are fantastical elements, the characters and setting should reflect real people and real places, because they're inspired from them.
I'm like you, hardly anything is original, though what I think makes a difference in one piece and another, and the originality of the piece, is the voice and style. I think it's essential that you find your own voice and style and use it, rather than mimicking other writers. This is only something that you can achieve through experience. And it will be effected by what you read.
Don't know if that helps or not. Use or lose.
For what it's worth, I started out writing fantasy. I think many new writers do. I wouldn't be a bit surprised if that doesn't change down the road, but if you're meant to write that genre then stick with it. But I would suggest reading fantasy, at least in-between reading other genres.
