My style has matured simply because the more you paint the better you become. In addition reading through Games Workshop painting books which are not bad and scoping the explosion of information on the internet I learned more about what I was trying to do. You probably can see the biggest change in the base of my minis. I still don't believe in spending forever and a day on bases but I certainly don't want the base to be neglected to a sprinkling of flock and glue. My current style shows more depth because as I learned more about my hobby I learned more about how to paint.
If you don't think your a good painter just keep painting and you will see the difference. There is no magic solution it's just a matter of time. Today there is more then enough sources of inspiration and instruction on how to paint on the web to keep you occupied for some time. For me the first sign I was finding my own style was when I wondered away from Games Workshop products.
Now I'm not saying GW doesn't have good hobby products but when you first start and have no glue how to get started GW products are naturally the first thing you use. As you start to learn your way you become curious as to other options and through the internet you will hear plenty about those other options. At one time I used only GW paint and brushes these days I use very little GW paint and learned about Winsor and Newton Series 7 brushes. I mainly use Vallejo Game Color and Reaper Master Series Paints. For certain things I use Golden Fluid Acrylics a nice paint many people don't know about. There's nothing wrong with using GW citadel paints as long as you know there are options out there. Use what gives you the best results. The bottom line is with time we all get better. The only way to become a better painter is to paint and take time to look back so you can appreciate your own growth.