Nobody replaced Syd Barrett one-for-one.

The band reinvented itself collectively. After Syd’s departure, Pink Floyd moved from psychedelic pop to sprawling concept albums, and the songwriting duties fell to Roger Waters (lyrics, bass) and David Gilmour (guitar, vocals). Waters became the primary creative force through Dark Side of the Moon and The Wall, but it was never a direct swap — Syd’s quirky genius was irreplaceable, so they simply built a different band.

That pivot worked out okay.