I think they are a symptom of an underlying problem: building a product not for yourself, but for some imagined customer and need. It puts your product in peril

I think they are a symptom of an underlying problem: building a product not for yourself, but for some imagined customer and need. It puts your product in peril because it adds guesswork. But if you have to do it, personas at least challenge you to put yourself in someone else's mindset.