Except BTTF doesn't mention gays or trans people. If it did, you'd see a lot more of the major cultural shifts, especially surrounding trans rights and trans acceptance.

It also doesn't focus as much on television, except to the extent that people in 1955 apparently didn't know what a "rerun" was. (Did they in reality? Honestly don't know.) The other side to that is, back in 1985, if you wanted to see an old episode of I Love Lucy or Gunsmoke (which had actually gone off the air by then, I believe) you either caught the rerun of the one episode some network was broadcasting or you were SOL. I'm not sure anyone was even selling video tapes of episodes back then, even assuming you were one of the comparatively few people to have a VHS or Beta player. Your cultural library for recent-ish pop culture was about a millimeter deep, compared to now.

So, yes, 1985 is closer to 2015 than 1955 was to 1985 in some key ways. Some of that is because you can only repeal Jim Crow laws once. Some of that is because Netflix has Punky Brewster on demand. Some of that is because most people are neither gay nor trans.