How experienced, how talented, and how successful you may be as a writer are other questions, of course. But no matter where you may be right now, you can always gain more experience, nurture the talent you have, and acquire skills that you don't yet have. And it's not your responsibility to live up to that person's criteria. The words you've put on paper or disc are all the proof you need that you're a writer. And no one else can ever take that away from you.
Every writer starts out as a beginner.
All of us begin our educations without knowing how to read. And every one of us who writes is or was a beginner at some point. Being a beginner is nothing to be ashamed of or to apologize for. It's simply an acknowledgment of where you are right now. Throughout history, every writer who created something grand and wonderful had to first write dozens, or even hundreds, of pieces that were anything but grand and wonderful.