The problem is that if you're going to talk about declining birth rates, it's millenials who are currently in the age bracket who are responsible for producing most of the kids in society - with xennials taking up the tail end of that. Gen X at this point are in their mid-late 40s or older so their child-rearing age bracket days are well and truly coming to a close. Meanwhile Gen Z are really only starting to form the front end of that child-rearing age bracket. They're specifically mentioning millenials, because it is millenials who are the ones who, if birth rates were higher, would be rearing and raising the majority of kids in society. When birthrates aren't happening, it's because we're not having kids.
Likewise, many women are putting off kids til much later in life (in fact you're starting to see the odd regret story about women who missed the window and now regret it), which likewise is going to lower the numbers of women who aren't having kids.
No matter which way you slice it, those are the reasons kids aren't here.
Because the article is about "What is a major reason Toys'R'Us is citing for loss of business?" not "Why aren't millenials having children at the same rate of previous generations?"
Is that a possible response article? Not really. The reason is that if you were going to truly look at those reasons, I'm not sure a mere article would be long enough to do an exploration of those issues justice.