I have been entering contests since the mid 70s and I have never heard anyone tell a builder that his entry shouldn't even be entered because of the way it looks.
I have seen judges at the regionals and nationals walking around with the actual aircraft manuals to see if the model has what the real aircraft had on it. One had a book of pictures so he could check to see if the markings were accurate down to the smallest detail and heaven help the modeler if it didn't. Some people are just that way. I got stuck with a guest judge one time that started talking about a model we were approaching. He said he was getting tired of seeing this kit entered all the time and it never won anything was wondering why this person that he knew kept entering it. I immediately called for a main judge, explained what just happened, then explained that this was the first time it was entered and I was also disqualifying myself because I can't judge my own model.
Anyway, go ahead and enter. Do it for the experience if you want, do it for the fun, but do it if you can. You get to meet all sorts of people, get tips on how to do certain things you are interested in, maybe find a kit or decals, or detail set you have been trying to find or didn't know was available. Before I started going to and entering contests I would build a model and then what. It would sit on a shelf until I got rid of it someway. Most would go to recruiter's displays, but many would just sit there. As they did I would wonder if it was really any good.
At the contests you meet all sorts of people who can tell you little known facts or general information about your subject that you might never have known otherwise.
If you don't win, you don't win. It's not the end of the world or your building life. Believe me, I've been building since I was five in the 50s and I have lost plenty of times and still keep coming back.