What's that you say, it doesn't feel like you're doing better work? Your in-box still collects all those disheartening rejections? No matter.
Seriously. Here's the evidence:
Pull out something you wrote years ago, way back when you first got the urge to write fiction and began putting pen to paper, or fingers to keyboard, or whatever your early method was. Start reading through that piece. Do you see stuff in the first few pages, or paragraphs, or even sentences that makes you cringe? You would never make those rookie mistakes today, would you?
Well there you have it! These are all signs that you've honed your technique, at least to some extent, given that you know at least some of what needs to be improved. Yeah, figuring out the best way to transform that early effort into a story you'd be proud of today is harder. But heck, I bet you have a few thoughts on how you can improve it.
Now, I'm not saying that early piece is thoroughly professional, even with reworking. But then again, you never know. It just might be. I once sold an early story after it sat around for twelve years. That was how long it took me to figure out what it needed.
Give it a shot! I wish you the best.