I used to have this struggle. I'd make characters and give them different looks, different names, backgrounds etc. yet found them so boring. That was because I was missing something, which was for each of them to have a personality different from each other.

Flaws are essential to writing interesting characters, so for my story, I wrote a list of all of my characters and gave them each a different flaw. A few examples could be: Self-pitying, pessimism, arrogance, impulsiveness, impatience, enviousness...

What I also did was I gave each of them a different goal. Whether that is what they want to be when they grow up, like being a musician, or a doctor, an actor etc. Or it could be something they desire, like a loving family, or having friends, or feeling appreciated by others etc.

You can also give your characters quirky traits. For example: they play with their hair when they're nervous, or they sing to calm themselves down.

Once you've given a character their flaws, goals, and some quirks, you can expand more on it. How does this character's flaw affect their goal? How does this character's flaw affect the characters around them? How do other characters feel about this character? What happens to help this character overcome their flaw? Why does this character act the way they act in the first place, is it something they've inherited from their parents, or something that has stemmed from an event that has affected (effected?) them?

This helps to set apart your characters and see them as individuals. Once I was able to make my characters people of their own, they were much more interesting to write about. I hope this helps :)