Poor posture can be slowly changed and it is life changing, obviously worth it.
Surprisingly the tongue has some major effect on posture, especially on forward head posture. There are all sorts of tongue exercises that benefit breathing, posture and even the looks. Tongue should be basically resting behind top front teeth and slightly press up the palate. For exercises look up muscular imbalances and see if you identify any on your posture. But all things start at the feet though, if feet have a problem the whole chain up gets affected so pay attention to the whole body.