I worry that my writing style is boring. I worry that I describe things so ineffectively that my readers' eyes will glaze over and they'll be unable to imagine anything, that the experience of reading it will be drier than an encyclopedia, and that I'll never succeed at the art because all I'll ever achieve is words on a page, meaning nothing to anyone.
I also worry that my characters are all flat and lifeless, or that they're all copies of each other.
It looks like these are common insecurities, though, so I'll share the two things I've learned about these along the way.
First: Another writer once let me in on a secret. That is that every writer thinks that their own writing is boring. The reason for that is that we already know what's happening next - not just in the plot, but in every sentence - so nothing is surprising or fresh to us even when we first put it down on the page.
As writers, we can next to never experience what it is to be a reader of our own work.
Second (which I learned myself): We see or imagine similarities in our characters that readers never do.
I found this out years ago, when I confided in the friend I play RPGs with that all my characters felt the same. She was utterly confused, insisted that they weren't, and then said that it was her characters that were all completely the same. Which utterly confused me.
We've been playing with each other for years and you'd think we'd know each other's cliche character types, but we spent several hours hotly debating how the other person's characters were completely different, and every time one of us compared two of our own characters that we felt were identical, the other person would be like, "That's such a reach? They've got nothing in common."
In short... It's impossible to accurately judge your work as a writer. But that means that many of your writing's flaws are probably just in your head.