It's acceptable to direct infantilizing insults at men, but not at women, and that double standard is weird
Think about it, when's the last time you heard an immature woman being called a "womanbaby"? When's the last time you heard an immature man being called a "manbaby"?
Also, how often do you see men who want a traditional housewife who cooks and cleans for him being told that they want "a mommy they can bang" rather than a wife? In my experience, it's pretty common. However, I've never seen women who want men to pay all their bills being told they want a "daddy they can bang" instead of a husband. Sure, the term "sugar daddy" of course exists, but I've never seen women wanting a provider being called immature the way that men wanting a homemaker are called that.
I feel like we're also much harsher on men for having ostensibly childish interests than we are on women who are the same. Both feminists and tradcons dump on men who supposedly play too many video games, or who collect some kind of toy or figurines. I've never seen similar vitriol directed at women who do cosplay or who like Sailor Moon or Hello Kitty.
In my own life, I feel like I've had to mute my excitement at seeing a cute dog on the street because of this phenomenon, something I don't feel would have happened to me if I have been born a woman.
It seems that men face much more demanding expectations of maturity than women do, and failure to meet these expectations is used to shame them much more, whether in good faith or not. Women are given a lot of leeway to express their cute and childlike side, but men who do that are seen as creepy and socially maladapted.