Of course you can “manage in life” without knowing how to make cake. But that is not why it’s not “important” to know how to make cake. It’s not important because, well, it’s not. Why don’t you tell me why you think it IS important and we’ll go from there.
I don’t believe that if a girl goes to a gadol (R’ Shach or R’ Kanievsky or whoever it was) to ask a question about a Ramban, that that means that she plans to spend her entire life learning Ramban and will never take on any real responsibilities. I just don’t buy it.
On another note, this sentence:
“When someone gets married, they can’t spend all of their time learning Rambans, since they have to spend some time taking care of their families, whether that means baking cakes or changing diapers or spending time with your kids, etc.”
Also applies to men. And I guarantee you that no man who ever asked a shaila on a Ramban was told that some things are more important than learning Ramban and he should make sure that he knows how to make cake and potato kugel.