Humans are emotional animals, unlike Cthulhu—amoral to the point of psychopathy.
So far as Cthulhu cares, which is approximately zilch, marriage can occur between any two likeminded adults, regardless of gender. Or, depending on local healthcodes, between any two catsup bottles.
While the concept of marriage is outdated and somewhat insulting, the simple contract inherent within a secular civil union, granting symbiotic power of attorney between the two members of a matrimonial corporation, affords such permissions and taxbreaks that denying the option to a pair of people due to gender would be a form of inequality not seen in America since women and slaves were regarded as subhuman creatures.
Cthulhu’s position is simple: anyone and everyone can become connected to another adult in a civil union, while the more theocratic idea of marriage becomes relegated to the quaint, meaningless status of churchgoing; the state has no official opinion regarding religion, and therefore no recognition of religious marriage.