Shantanu Ganga story is a very important story of Mahabharata. Omitting it takes away the exact portrayal of a love deprived shantanu who loved Ganga very much and had to part ways just to prevent her from drowning one more of his offspring, it projects him here as a selfish who lusts after a woman half the age of his son. And moreover I agree the golden fish took away some time but I guess its because it was sayantani ghosh. If that's the case get ready for a over dose of princess amba also to be played by ratan Rajput.