Needing to learn a new tone for a new fandom is what keeps me from spreading out too far... it's both daunting and scary to try to write in a fandom you've never written in before... and then I worry that I'm making everyone sound alike and only the details separates the storied.

So writing shorter fic is a good start, it lets you do targeted pieces and you can focus on characterizations easier if you're not writing long, involved fic.

That's my encouragement to tell you that you're doing okay... when you have a better handle on writing those characters, those longer stories will flow easier!