There were many reasons it closed. The show was never updated, it closed once a year for a minor refurb and that was just for painting. Many nozzles were old and litterally crumbled from so much use. The lighs started wearing and several times prior to closing the show would pause becuase of electricity flowing through the water from the lamps leaking. The last time the show was updated was in 1991. if you have anymore questions let me know.
Disney even called in for a new show months after they tore it out, but Waltzing waters came in and said that the stage area would need to be rebuilt because Disney screwed up the fountain pool with their plants and new water system for the plants.
I'm imagineering a new signature for your future enjoyment!