In defense of disco, Nightwing's was never a disco costume. Dick didn't take on the Nightwing persona until 1984, by which time disco was long dead. I should know, I was king of the disco dance floor (circa 1978). And Superman adopted his Nightwing identity and outfit in 1963 when disco was barely a glimmer in Van McCoy's eye.
I never liked the George Perez design, but I think once other artists got rid of the extraneous decorations and kept it to the basic elements, then it served with distinction. But it was never disco.