I think that a lot of men these days really do want a "Mommy GF". It's more than just a meme. Many men (!!!) really do fantasize about, if not actually seek out, women who will nurture, protect and discipline them, and possibly also allow them to live vicariously and find an identity through their relationship with that woman. I think there are several reasons why that might be:
i) A great number of men are uncertain about, and lack confidence with respect to, their identity as men and their putative role (if any...) in romantic relationships. They conceptualize themselves as weak and hesitant, and so look for a strong (which today means female) presence to act as a counterweight in the relationship and as an anchor for their own unmoored self-conception.
ii) These men have bought into the facile but increasingly commonplace media representations of women as omnicompetent -- as superior to men in all areas of life. It is not surprising therefore that men would look to women as leadership figures, especially since men with this mindset are likely to lack the real world experience of socialization with women that would discredit these inane media depictions (and/or are unlikely to believe their lying eyes anyway).
iii) Gullible men buy into the feminist sop that upheaval in sex roles ACKSHUALLY benefits weak or unmasculine men by making physical, social or mental weakness or femininity in men more acceptable. This of course is bullshit. Weakness of any kind in men is still derided and regarded as a red flag by any woman. Women will declare their sympathy or solidarity with weak men inasmuch as doing so increases their own status or helps them to cultivate their own identities. "Sensitivity" in men is valued by women, if it is at all, inasmuch as it makes men more receptive audiences for the peevish whining of dissatisfied women.
iv) The reduction in social and cultural sexual dimorphism in the West has occluded femininity and rendered authentically feminine attitudes amongst women suspect and low status.
v) The concept of men and women in romantic and sexual relationships as helpmates who experience a specific type of bond, characterized by complementarity (rather than similarity) distinct from other inter-sex relationships (family, friends, lovers) has been replaced by a conceptualization of romantic partners as friends who fuck. Operating with this crassly traduced understanding of romantic relationships, the Mommy GF craver is free to imagine his idealized romantic partner more as a kind of hybrid fetished-other/fantasy-self rather than as a complete and separate person with profoundly different, but complementing, roles, outlooks and competencies to his own.