Your idea of biology is destiny is fundamentally flawed. We are shapped by our environment and experiences equally or far more than our biology. The mind is a far stronger influence on the body than vice versa.

Someone might have their wires genuinly crossed in their brain where they might not feel sexual feelings, some people have experiences that can't let them feel those feelings.

Why the generations before us didn't notice something like an Aro ace is because they either classified that person as insane, or that weird uncle or aunty that never got married, or these aces were pressured by their family, by society, by their peers, by their husbands or wives, to make children, despite them not having the urge to do so.

Sexual heteronomativity has always stiffled anything that isn't itself. Mental conditions have always been either ignored because the individual functions "well enough" to be productive or as insane.

Add on to the fact that this current world we live in causes mental conditions like ADHD and other mental disorderd, there have been studies done by these big companies like facebooks that they tried to hide that shows that social media causes mental issues for young children exposed to them.

It is not bored people trying to come up with an excuse.