If people tell you that you are an introvert, it must mean you are quiet and shy, withdrawn. I agree, their telling you that is a criticism. They're not complimenting you on your lack of personality. They're saying you are boring.

If you tell them off, you are then introverted and hostile.

As far as do girls like introverts or extroverts more, it's probably pretty balanced. An outgoing person usually partners with a more reserved one. Being an introvert isn't bad. But if people tell you that you are, yes, I think they think you are boring, and that can be frustrating to other people. You need to hold up your end of the conversation. You need to contribute something. Nobody likes to have to bring everything.