Well actually, Pink Floyd doesn’t exist anymore, do they? Really not sure. David Gilmore was the brains and his sound is what defined PF in my mind. Waters was just the bassist.
Here are some comments FWIW. You may know all this stuff ...
I have followed that band since 1969 when they were a largely unknown underground psychedelic band. When I saw them in 1970 I had no problem getting a spot leaning against the stage about 10 feet from David Gilmour. In 1977 I was way back in an arena.
I can see why one might think David was the brains of the outfit since he became the defacto band leader and face of PF after the split from Roger in 1985. But David wasn't even an original member. There wouldn't have been a PF without original guitarist and pioneer Syd Barrett. Of course David took the PF guitar work to a higher and more accessible level. The early Floyd sound was defined by all of the group members. It was one of the original jam bands.
Roger was hardly just a bass player. Waters wrote most of Dark Side of the Moon, Animals and almost all of the Wall. He gave the band a demo album of the Wall to play. He was a main writer even in the early days - Set the Controls, Careful with that Axe, etc. Waters was a huge factor in that band becoming famous and mainstream. Waters also took less drugs than the rest of the them according to Gilmour.
So while Waters is certainly an obnoxious leftist he was the main guy in that band up til 1985. Waters was the guy in the drivers seat in the studio control room when they recorded their big albums of mostly his songs. He ran Pink Floyd in the late 1970s and up til 1985.
PF didn't release anything of substance after Roger left and David's solo albums are hardly stellar. David essentially became the PF caretaker/leader after 1985. Of course (as you say) -- Gilmour's solos defined a lot of the "sound". I agree with that although the other band members also help defined the sound. But Gilmour's impact on the sound was huge. I followed him more than the other guys.
Having said all that -- Waters didn't produce much of anything of substance after he left PF either. So there was this synergy between Waters, Gilmour and Wright that made that band in the 1970s/1980s. The individual parts never equalled the sum of the parts.