Lack of any fundamental base, now that he doesn't have the athleticism or vigor from the past , he needs a strong set of reliable skills to lean on.
He never learned legitimate striking defense, never learned how to box effectively, and now it's a steep fall down.
Your not going to be 29 forever, so you need to start learning real skills that'll help carry you along at an advanced age, every single pro fighter should know how to throw an effective jab to help setup their potential offense, but also to help win rounds and keep these young aggressive fighters off of you. You don't need to have the best head movement in the world, but learn how to adapt an elite jab into your arsenal before it's too late.