It has been worth paying for a professional calibration for many years, now. Since the beginning of color TV, there has always been the need to and the ability to get a better picture by calibration. Early on, most people could do so at home. Now, with DVD's available, one can tweek settings fairly well but it is now very complicated to get the most out of your set. It really is best you get a professional calibrator who knows how to do so. The earlier OLED's could not be fully calibrated which frustrated several calibrators. My understanding is it now can be done but, to what level, I do not know.
Most people like their sets to look "good" which is not want you want. You want the picture to be an accurate representation of whatever it is you're watching. Usually that means lower brightness and lower color levels. The color accuracy and zero distortion is something that is extremely important, too. Sets are so complicated now that, in order to bring all these different aspects together for the best picture possible, you really need a professional to do so. If you watch 4K HDR stuff, then it's worth it. If you just watch the weather channel, then probably not.