What bugs me about this is that it is an application of English-language concepts of gender to a word in Spanish.
So in Spanish you would say: "literatura latina." That would be literature written by Latinos and Latinas: the adjective modifies the noun, which happens to be feminine in gender. The x is a way of neutering the gender. If the noun happened to be feminine, then you would say "feminismo latino."
From the perspective of speaking English, gender is only applied to persons and animals with a designated sex. So people think of Latino / Latina as only applying to people. Hence you need to say "Latinex" to keep things gender neutral. The word was invented by someone who doesn't think in Spanish.