There would be no Pink Floyd without him.
There was about a month or so Floyd had all 5 members with Syd Barrett and David Gilmore included. Once Syd left Gilmore became the main guitar focus and inspiration of their music. Their music style changed dramatically once Meddle was released and consequent album releases since.
Floyd wouldn’t have gotten recognized if not for Gilmore. Once Waters left the band Floyd remained top of the music lists and where did Waters move to... mediocraty