I agree with GP. It's a matter of finding a style that works for you. However - your work will look like yours at the end of the day. Illustration styles are like handwriting. I can spot Mike Schley's work or Jared Blando's immediately. You'll find your style.

For every piece I work on I can look at it afterwards and see all the pieces that I want to fix and know I'll never have time to. You spend more time looking at your own work than anyone else's. You'll inevtiably see the flaws in your work, because you were there when you made the mistakes. The best solution is to put your work up on the Guild and get feedback. And challenges are good for that. Not only do they get you feedback, but they'll also force you to finish things to a deadline. This can be a great way to get past cartographers' block.

A deadline requires you to make decisions, and that'll help you move forward. Some decisions will be bad, others will be good, and others still will result in happy accidents. I'd never get anything finished without deadlines, and the eternal dream of a map that I'm happy with will always remain that - an unattainable dream.

On a slightly more practical note - I know precisely what you mean about levels of finish. There's a difference between the polish in a map that you see in many publications and a personal map. When I'm working on a new style there's always that point where I look at what I'm working on, and at the reference I'm using of where I want to be and see a huge gulf. Mine looks like a bad drawing and that looks like a map. The only way to get passed that is to push through. The odds are that you're one level of detailing away from where you need to be. Jump back in at 100% zoom, add a new layer, and start digging in. Don't be afraid to colour sample from reference and keep a copy of what you're working towards right beside your image.

And as for mimicking the style of others? Lots of illustrators learn by trying to recreate the work of people they like. You'll learn things as you go along. But using it as a learning exercise is different from subjugating your own style to someone else. Take what you can from each person and integrate the things that work into your own work flow. Ditch the rest.