Would really rethink probably how it looks yeah; because the cover doesn't really tell me alot that the comic is actually about. If you didn't tell me it was a superhero comic I would've thought it was a slice of life/drama romance comic just based on the cover and name alone.
So yes, I would look at other super hero comics you like and start from them in terms of understanding what makes them work and how you could implement those same elements in your comic
I was in the same boat with traditionally drawn covers too, I still draw traditionally but I do alot of clean ups in digital just to make it look more professional and appealing. (Traditional has a tendency to get messy if you're not careful and can look even messier on a screen which is why digital clean up is usually essential)
Here's two of my covers, both traditionally drawn but the second one being heavily retouched in digital clean up.
This same concept can be translated to your thumbnails too.


Can't tell you how much more attention my comic has gotten just by this slight shift in focusing a little more in digital clean up....
So yeah, traditional art isn't the issue. it's probably just you needing to clean up a lot of it just to make it more presentable and eye catching to potential readers.