Asexual does not and has never meant "not interested in sex". An asexual person is someone who doesn't experience sexual attraction. It's a sexual orientation.

--Heterosexual = Sexually attracted to opposite sex

--Homosexual = Sexually attracted to same sex

--Bisexual = Sexually attracted to both

--Asexual = Sexually attracted to nothing and no one

(To put it simplified.)

This meme is about someone coming out as asexual (= does not experience sexual attraction) and some asshole is telling them that they're not actually asexual but that they don't feel sexual attraction because of trauma. More often than not, no such trauma actually even exists. But people who deny the existence of asexuality insist that it's not a real sexual orientation, and if asexuals got over this non-existent "trauma", they would be "cured" into being "normal".