Bike fitting fits the bike to you in the fitters opinion. Whether this 'solves any problem' or not is a shot in the dark on their
part and a leap of faith on yours. An hour or so on the fitter machine may or may not translate to something at 40-50 miles
down the road on the bike.
There is some truth in this, however, there seems to be many more people who have had a positive outcome than those that did not. A qualified fitter will fit you based on body geometry and your issues, not on opinion. With a good fitter, if your problems are related to fit, you have a better chance of resolving your issue than not.