More fun with Google's Ngram Viewer. Here's gay, lesbian, homosexual, and queer. After a slow rise in popularity starting in the mid-1970s and a surge in visibility from the later '80s through the PC-related culture wars of the early-mid-'90s, gays and lesbians have started vanishing from the popular mind. I mean, we know they're out there -- we just don't care anymore.
The only term that's still on the rise is "queer," but it's nowhere nearly common enough to make up for the plummeting emphasis on "gay," "lesbian," and "homosexual." So, it's not as though this chart merely shows that the fashionable term for people who like someone of their own sex has become "queer" instead of one of those other three.
How about issues central to the gay movement? Here's HIV and AIDS. Again a falling interest since the mid-'90s. And here's homophobia and gay bashing -- same thing. There were moral panics surrounding these things for about a decade, then people realized that much of the scare-mongering was either bogus or exaggerated, and they stopped paying so much lip-service to them.
The only gay-related term that's been steadily increasing in prevalence since the '90s is gay marriage. However, this is a civil rights issue that just so happens to deal with gays, now that the more egregious civil rights matters have been taken care of. In contrast, AIDS, homophobia, even the designator "gay" itself all relate to gays per se -- what makes their identity and behavior different from everyone else.
So, the identity politics part of the gay movement has totally evaporated, as they realized the straight majority had stopped caring. They had no choice but to take up some civil rights issue like gay marriage, which the average person might take the time to listen to.