This discussion is not about if the current prediction methods are good or not, it's about if we should even try to develop these methods to begin with. How many cancer researchers would there be today if you had to cure one yourself, with no grants or outside ressources before you are even allowed to enter the field? Probably not a lot.
Your argument is a self fullfilling profecy. You justify preventing them to research how to predict earthquake by saying that they have not already predicted one.
Maybe in a couple of decades we will find out that many of the big ones could have been very easily predicted, maybe not. The way things are going, we will never know.