If your nieces weren't interested in the sets Lego should have focused on better sets that were still gender-neutral. That doesn't exclude zoos, camping, or pet orientation.
What it does exclude is antics like cancelling my friend's "tomboy"ish daughter's subscription to Lego magazine and sending her Lego For Girls Magazine instead, to her great upset.
Toy gendering is stupid and inane. Lego should have nothing to do with it.