>I don't see any material reason to believe that Foucault et al. really
advanced these movements.
It depends who you ask, but a great many 'non-academic' people highly invested in changing the lives and contexts of gays and lesbians and other groups kept on the outer by ideas about heterosexual normality have found Foucault's own work and/or the work of people influenced by Foucault exceptionally useful. The same appears also to have been true of Butler. I am not sure on what grounds you are dismissing this.
Catherine