You are not alone! My friend who is already in grad school read my SOP, and she told me to write about something that is already in the established disciplines - to enter the discourse, so said she. I used writing an SOP more as an opportunity of self-expression and listing my interests. I feel like I did not address a specific topic that I want to work on. Now when I look at it, my SOP is more like a PS for college, which is actually more fun to write. Maybe check out what other people are doing with your interested topics? Or what the professors are working on?