We suggest you write about something personal because a theme or experience that’s close to your heart will keep you motivated and your passion will shine through in your script. That said, if what fires you up is something that lies outside your personal experience, go ahead and write about it. Educate yourself on whatever it is, so you’re writing from a place of knowledge and respect.
More than likely, what intrigues you about your topic is what makes it personal to you. After all, Bong Joon-ho probably hasn’t pretended to be an Art Therapist to earn money from a super-wealthy family (Parasite) and Greta Gerwig probably hasn’t traveled back to the 19th century (Little Women). In these cases, it’s the socio-cultural and emotional aspects that make the work personal.