As an artist you have always two options - appeal to yourself or appeal to an audience. If you appeal to self only - you may feel inferior, but when you appeal only to the audience you may feel empty and shallow inside. Regardless of the need to share, I think an artist 1st has to appeal to self and feel happy about creation process and only then and after worry about others.
Are your characters boring to you? If they bore you, then you need to find some other subject. If you are worried about audience, then stop worrying unless arts is your day job. When you just hobbyist and draw for fun, then sop worrying and do whatever you like. Also many artists draw very similar things - be it one fandom or even one character. Admitted even most skilled artist becomes boring to watch, when their gallery is full of just one fan art gallery, but if its what they like then not my place to judge.
I think it's good to draw what you really want to, and drawing the same characters and repeating it isn't bad. many years ago I draw fewer original characters and I tend to draw the same character, on this character I've drawn over a hundred time but I enjoy drawing him and I want to draw him more.
and I feel it's not fun to draw what I don't want to, so to force to draw the different character is harsh way. I focus on enjoying the arts, the favorite characters and not difficult art style, it make me draw more and more arts and it give me the art improvement. now the original character is increased and my frequent character become not frequent.
I have the similar fear of always staying in the same spot with my art when I keep drawing the same thing over and over (mainly my OC's)
If that's what you're looking for my advice is to keep drawing what you enjoy the most, but with every piece try to stretch your comfort zone a tiny bit: poses, angles, colors, line style etc. That way you can stay in your zone, but at the same time slowly gaining the experience in new things.
nothing wrong with dabbling, but if you feel comfortable in what you draw then don't be too stressed about it. I have seen artists that focus only on one thing, pattern, etc and they all look good and unique in their own way.