I can't stand when "first ever" is done with something incredibly minor like what Disney does when they have their first gay character in each series who is edited out for Chinese audiences. Or in the third recent Star Trek movie where they made a huge marketing fuss about Sulu being married to a man and then it only appears for half a second in the background of another shot. Or some semi-recent Cartoon Network show where two dudes danced together in the background of a scene at prom. It's the kind of stuff where it has absolutely no relevance to the work at hand, but the media hypes it up for marketing points.
I think it's when minority characters are shoehorned into an existing property that it gets me miffed. Not because they are doing anything wrong, but because they are always doing it for the wrong reasons, which is "a few headlines."
On the other hand, I love it in media when it just sort of happens. Someone's always got to be first, but what about second and third and fourth? Steven Universe made waves for its queer representation, and that was always the subject of news and such, but the show was never that popular. However, that show being first is what allowed so much other queer representation in animated media over the past five or so years. And the representation has gotten better and better!
It's the same thing with certain cartoons in the 90s finally featuring Black, Latino, Jewish (and sometimes even Asian) main characters that paved the way for the explosion of diverse casts throughout the 00s, with so many shows I'd have trouble listing them all. (Hollywood ALMOST went down that path, but in the 00s they decided to chase four-quadrant blockbusters and back came all the generic white dude protagonists for everything.) Nobody really remembers what came first, even if there was a fuss about it at the time, but it's vital that they came first, because something always had to.
So, I love representation of all peoples in all groups, but I hate when that fact becomes a huge marketing point for stuff that doesn't actually deserve it.