Then there are guys who have one single bad role model that they will not stop emulating. For some guys, it's their Dad. Think about how your dad dressed when you were growing up. He probably was working hard to support the family and had little time to think about what he was wearing. He may have been totally disinterested in his appearance. You may have picked up some of these ideas without even realizing it. That's why it feels so hard for you to take an interest in your appearance. It feels likes you'd be changing into a different person. The truth of the matter is you are not your dad. You are not defined by your own disinterested, dismissive attitude about your appearance. If you changed this, you would be a better, more effective person.
Perhaps there was a time in your dad's life when he had a great look, but you just came along too late to see it. Ask yourself this:-did you see your dad in his prime when he attracted your mom? Or did you see him 10 years later when his style was functional and pragmatic? Ask your dad sometime about how he dressed when he was trying to meet your mom. You might find that it was a lot different than what you saw him wearing around the house when you were a kid.