English as actually spoken is not gender neutral. While the language itself isn't gendered, the way it is used is not.
Now that you can see where I am coming from that English at it's core is not a gendered language I will try to explain why it seems like there is still a masculine and feminine divide. There seems to be a strong bias in the way that words are used so that men are on top and women are on bottom. It isn't something that people intentionally say to their kids but if you stop and look at the message the words used you can start to see why people internalize certain feelings.
There are some things that are reinforced for gender, especially to children. Phrases like: "Man up", "Grow some balls", "____ like a girl", "Sit like a lady", etc. The kids hear these phrases and come to their own conclusions about the deeper meaning. Boys are tough, boys don't cry or show emotion. Girls are weaker and less capable, girls are dainty and fragile. There are stereotypes that are positive and negative and everything in between.
Instead of hyper specific examples like this though just think of the daily interactions you see around you or in television or movies. How are the men described? How about the women? Say a server comes to take your table's orders. Unless it's a table of all women they might say something like: "Can I get you guys something to drink?". The default is guys. Maybe a forced example. How about when you talk about someone that you saw at the store? An attractive woman becomes "A hot girl". Would you say the same of the attractive man? Would you say: "I saw a hot boy" or "I saw a hot guy"?
This is where I think the main issue is for me. Girl is the opposite of boy. Girl is also the opposite of guy. Women never seem to grow up and be respected. Calling a male in his 20's a boy is an insult. Calling a woman in her 20's a girl is totally normal. Women appear to have just two descriptors: girl and old lady.
If you made it this far I applaud you for reading my ramblings. I am not able to make the clearest argument about this topic. It is more of a collection of thoughts that has been swirling around my head for a long time and something that I feel like most people don't pay attention to generally. With the changes in my life I have been somewhat forced to notice the discrepancies in the way that men and women are treated by society and by each other. In the language used when interacting with others.
I don't have a solution or some flash of insight into how things can be improved, as a whole. Just try to look around and notice how people describe women and men. Notice the cases where men are assumed the default, even if the majority is not men. Try to imagine if the same description was used for the opposite gender how the message might change. Biggest of all try to think of the message that is being suggested to people when these phrases come up. Is that the message you would like children to take away?
I can't point to a specific word or phrase that made me think of these things. They are all around me. I can say that I have internalized a million different phrases that say that women and men are not equals.
When you use one gender as an insult to the other how can they be equal?