If you are that writer, I believe it is important for you to review why you want to write. If it is to get rich, then you have chosen the wrong career. But if you have talent and something to say, then your life will be incomplete unless you do write. So, you have no choice. Age is relative, especially when we break down the different areas of the entertainment industry.
Age is a bigger topic in television than in features.
And series television writing is where ageism has the most impact. Because it is perceived that one must be young to write those half-hour and one hour shows with characters under 30 or even under 25. These are the shows where it is perceived that the writing must be topical and from a youthful perspective. Those shows should be and often are age-blind. But most of you are not aiming for a career in television.