Trek being a window to humanity looking beyond it's own bigotry and selfishness is it's biggest appeal to me. The build up has been incremental and a reflection of our own progress over the decades. Quite a ways to go, of course, but at least for a while things have been looking up.
Another reason I loved the show Schitt's Creek. David (pansexual) just was, and everyone just accepted it. Again, no explanation or apology. It was charming as hell.