I hear authors always trying to justify why their story should be published and they always go back to the time they spent on the story, or the number of rejections they have had with prior projects. It seems that there is this belief that the time you spend is the only thing that matters. The reality is what you do with it.
Think of it this way. I have heard "athletes" (and I put this in quotes for a reason), talk about the hours they spend at the gym perfecting their craft. They proclaim nearly Olympic athlete status, and yet, when you watch them in their sports, they are far from good. Why? It wasn't about the time they spent at the gym but what they did at the gym.
My daughter just joined a new dance team and I am seeing the same thing here (as well as hearing it from the other "Dance Moms"). The people who have been there for some time, try to act and behave as if they are the end all be all! The reality? Nothing to cheer about! And why is that? I watch them from outside of the studio and when they are not being watched by the instructor, they are goofing around and not working on their skills. Outside of the studio, you hear the moms talking about getting their kids healthy and really prepared for the season, and yet, as the kids come out of the studio, mom tosses them a McDonald's bag.
We often like to use the phrase, "practice makes perfect." The reality is "PERFECT practice makes perfect." Again, just going through the motions is not going to fix the problem. You have to critique your own work. You have to find your mistakes. You have to fix the problems.
Look, if you are getting rejections from editors and agents, there is a problem. It is not just a situation of "paying your dues." The story may not be right. You have no idea what you are doing. You are submitting to the wrong person. You are submitting projects that are not marketable... the list goes on and on. I can promise you that your manuscript does not have an odometer on it and when it reaches a certain number of rejections, your story will sell.