Literally no-one finds Gen X interesting enough to even come up with an insult, except for all Gen Xer's, who know that Gen X was indeed the best generation by virtue of our disaffected and intelligent nature :)
I identify very strongly as Gen X, and no under 40 gets to shove me in a category with my own mother!
But seriously - ageist, sexist, entirely lacking in an understanding that 'people like you, whatever you are like' have been present in every single generation, that the Boomers were full of protestors and activists, against war, against homophobia, for women's rights, for the environment. That people who use 'OK Boomer' are coasting on Boomer activism.
Now, personally, coming of age in a recession, I have my own set of resentments about Boomers - but get real, they were lucky in some ways, unlucky in others, and plenty of Boomers missed out just as plenty of non-Boomers missed out.
It's so immature, the whole thing.