I think that's a question that most artists ask themselves from time to time. We make work that doesn't sing to us, we seem to be lacking in new ideas, and people seem "ho-hum" about what we do. It's easy to let that fear of being boring creep in.
Rather than tell you "You aren't boring!", let's break up what we are doing.
1. Very little is actually boring. I've seen paintings of simple pastoral life that made my heart race. You don't need starships exploding off the arm of Orion for your work to be engaging.
2. In the wrong hands, almost anything can be boring. I find 2/3rds of the work out there I see "boring", mostly because I've seen things just like it dozens of times before. Someone who isn't "in the business" won't have that same reaction. This brings us to a common point - Who are you making work for? If you want art directors to respond, you have to acknowledge that they've seen the obvious stuff many times, and might be tired of it. If you want the public to respond - Go with the with obvious stuff. There is a reason wedding magazines have a 3 year cycle for basically the exact same articles - your public will consume it, find value in it, and then move on. By the time someone is bored, you will have hopefully found new people.
3. Is your work not up to the level it needs to be to engage the audience you want? We will drill into this one, 'cause I think it's actionable and worth addressing. You might not be skilled enough yet for the markets you are trying to engage. Either you try and fail in the execution of something interesting, or (and this is what I struggle with), you stay with what is *safe* when you conceive of projects, so you don't get that last 20%, which is the part that gives all the *oomph!* to a piece.
Ok, you're not good enough. We can work with this. You gotta take a long, hard, and probably painful look at your failings though.
At the highest level, do you have the painting/drawing technique you need to execute your vision? If not...keep practicing. You're going to fail 1,000 times before your make consistently boring work, and then you're going to make 1,000 boring paintings before you get consistently interesting.
If you've gotten past the "abject failure" stage and to the "boring" stage, what is holding your work back?
If you can paint/draw components that really work, but the whole is failing, you probably need to work on your composition, and your "drama." It's beyond the scope of this post to give suggestions on that, but people like Chris Oatley have classes and schools dedicated to learning "Painting Drama." The good news is, this is a pretty quick fix for most people. Once you learn where you're going wrong, you should be overcoming the boring problem pretty quickly.
Next question - Are your designs stale? Do your soldiers look generic, and your aliens elicit shrugs from viewers? I have a couple of suggestions, and these are things I'm working on myself.
First - USE MORE REFERENCE. The biggest cause of boring designs is a lack of the details that make things feel authentic.
Second - VARY YOUR SOURCES. If you want to make cool designs, you need to look past the things you see every day. Don't copy video games if you want to make cool video game characters. That was fine when you were learning the techniques, but now you have to expand your pool of sources. Try to pull from real life. Use photos when you can't use your eyes. Don't spend too much time looking at other artists' work.
Third - GO OUTSIDE WHAT IS OBVIOUS. The easiest, and most common way to do this is to include elements that, at first glance, don't make sense. The easiest way to train yourself to do this is to create lists of elements, and then randomly combine them and force yourself to do something cool with them. If you are a character artist, I highly recommend the Reckless Deck for this. You can come up with the same thing for props and environments, just make some lists and then roll dice to pull elements off of them. The other thing I recommend is to make sure you are pulling from sources you don't know very well. If you put the same ingredients into the same soup every day for dinner, you're going to get bored of it. Think of something that terrifies you to draw, and incorporate that into your design.
Fourth - EMBRACE MISTAKES. This is one reason I love drawing and designing with a fountain pen. You can't erase anything, and you have to work with the lines you put down. There have been times where I deliberately just gashed out the ugliest line I could think of on top of my half finished design, because it required me to work in new ways to fix things. The eraser is the arch-enemy of interesting design. Perfection is achieved at the end, not during the process.
Thanks for reading, I hope this helped think through some of these things - If you can think of another cause/cure for boring work, I'd love to hear about it :)