Clayton Christensen (guy who wrote Innovator's Dilemma) has a pretty good debunking of the "target user" approach, telling us to instead focus on what job users intend to do with your product. Tells it through the story of trying to figure out the idealized milkshake buyer: https://youtu.be/f84LymEs67Y?t=27s
This whole idea goes by the name Jobs to be Done. Intercom has a sick PDF book on applying the concepts to product development: https://www.intercom.com/books/jobs-to-be-done