Your question is actually identical (apart from some minor details) to the one every 14 year old since the beginning of time has asked, and ever will ask, including your own Mom, grandma, all your teachers, and some day your own children and grandchildren. But your question is earnest and shows that despite your naivete you are probably more intelligent and more sophisticated than most 14 year olds. So I'll give it to you straight--no BS like "someday you'll understand" and "they really have your best interests at heart" and "you're too young to understand," etc. BTW, all those things are true, they're not BS, but I'm sure you've heard them all before, and like most 14 year olds, you've already discounted these things in your assessment of the situation. So I'll try another way, if you promise you'll at least try to believe it might be true. Since you posted the question, I assume you're open to anyone's answer, even if they're not "with you."
As people go from age 14 to whatever age your parents are, sure, they see things, learn things, observe things, and experience things that might shape their view of the world a little bit. But nobody really goes through the massive titanic shift in their beliefs that you think your parents did. Become lame? They didn't "become" anything! They're basically the same people they were when they were your age, believe it or not. And here's the kicker--would you believe it if I said that your parents are not only "not lame" for treating you the way they do and the things they say and believe, but are quite likely very cool and would be considered by many people of all ages to be much more cool, reasonable, in touch with the scene, and know what's what in the world, the neighborhood, and your school, more and better than you?!
And just don't write me off as another old fart that just takes your parents' side on everything, I don't even know them or you or anybody. Instead, promise you'll try one experiment. Sit down some time for a few minutes with your mom (or dad or both). Pick a time when you're not in the middle of some big fight about something, and make sure you have some time without interruption. (No phones, texts, tv, etc.) And have a really honest talk about just one thing. (Maybe the makeup, the earrings, maybe even what it means to be slutty.) Set aside everything you've previously heard them say--pretend it's a stranger that's their age and has a random 14 year old kid and you're interviewing them for the school paper or whatever. And you keep yourself in check and really, really try to listen to them and try to understand why think their 14 year old shouldn't be allowed to do this or that but it's ok to do something or another. Forget that it's about you for those few minutes and ask them to be super honest about exactly why and for what reasons they decide something you don't understand or don't agree with. You might actually find (oh no!) that there actually is a good reason for something, but you never knew because you never asked and were too busy trying to find a way to get around it. And, if you maintain your composure and they do too you might find that the reason for something is because they think something specific is true which isn't really true. And if you can tell them calmly and prove it they might change their mind about it, because their decision was based on it and it turns out they were mistaken. Here's another thing you probably won't want to hear, but think about this. Pick something you've argued about before (the earrings, the mall, whatever). Think back about the argument you had about it. You had all your reasons for wanting it, and they had all their reasons for saying no. Forget about whether anybody's reasons were right or wrong, or whether you agreed with their reasons or whether they agreed with yours. Ask yourself this: who was more HONEST in the argument? In other words, which side was giving the reasons they actually believed were the real reasons? Even if the reasons may or may not have been factually bogus, who was keeping it real by saying what they really thought and who was stretching their side of the argument with points that weren't really the truth but might lead to winning the argument?
OK, that's enough. My answer was even longer than your question. But good luck. And remember most of all--your parents "get it" a lot more than you think. They not only know more about things in the world and are trying to help and protect you, but they ALSO know how angry and frustrated you are with them and they TOTALLY know exactly how much you think they're out of touch and they understand very well what your life is like and how they look to you through your eyes. Your parents are NOT lame. And they totally know that YOU think they ARE lame and they totally know WHY you think they are lame. And yet they love you anyway.....that's how "not lame" they are!