IMO you can't compare wine or writing pens to mixing. Not sure you can really compare college education either as that involves many more people and other factors than just a mix engineer. There is definitely a level of non-suck that makes any mix listenable but a good mix engineer can take a song to a whole new place than what the producer or artists imagined. If that is what you are looking for in a mix engineer, their input and creativity then, yes very worthwhile and no other mixer is going to give you the same end product. Mixing is an art form just like playing guitar or any other art. Are you trying to say there are no masters in the mixing world? That makes no sense.