For me, it can actually be a little reassuring to be unsatisfied with my work, as odd as that may sounds. It means that I still have somewhere to go. My worst fear is hitting a point where I don't have that next step in front of me.
If you're unsatisfied with your art, that means you're able to see flaws in it, and that means you're able to do something about it. The feeling that your art looks boring is more difficult to fix than anatomy mistakes or getting better at character design, I'll give you that. But you can still work on it and change it. I used to be unsatisfied with my style because it was generic manga, boring and I was even slightly embarrassed by it but I thought "well I can't change that, it's my style. I'm stuck with it". I've learned though that this is silly. Of course I can change my style if I don't like it.
I suggest broadening your horizons. Research different types of styles that your normally don't go for. Go on Instagram or Tumblr and look for something completely different than what you usually look at. Analyze the ones you like the most and ask yourself "What is it exactly about it that appeals to me?". Look at incredible, fascinating pieces and try to figure out what this piece has that makes it interesting that you don't. Is it because the picture is telling a story, an emotion? Is it because of an outstanding use of color or shading that makes things pop? Is it because it's a quirky style that's nothing like anything you've ever seen before? Is it because the artist makes complex detailed backgrounds? Analyzing and questioning what makes a good piece and more specifically what appeals to you exactly. When I was struggling with my boring style problem, I even re-drew pages and pages of the best artworks that I loved in a personal secret sketchbook, to see if something felt good. It's this way that I discovered I have a ton of fun drawing very flat, very stylized art, akin to children's books illustrators.
It can also help to get new eyes and opinions on your art. It can be difficult to hear, but it can make you realize things about your art. Even if you can't see what your art is lacking, maybe someone else can!
That's how I personally deal with feeling mediocre, I take it as a sign that I'm still not done with my journey. To me that's a good thing, because I love this journey and I'm afraid of getting to the end.
I'd be really curious to look at your art and see if I can find something. There isn't a link on your profile or anything, but if you're interested feel free to send me some art, I'd love to look it over!