I didn't win the national champs because I wasn't good enough - you can't "buy" talent no matter how hard the training
"Scientific training" is certainly hard and unpleasant, but it is also "short"! Therefore is has huge advantages over long miles, fixed wheel, 27" steel wheels, saddlebags and bricks!!!!
Actually - to go back to the OP's question - fixed works really well as a part of a structured training programme - which really means that as a training tool it's probably most valuable when you're training solo and hitting some very personal, tailored training goals. It's also excellent for training on the rollers, again as part of a structured programme.