People are going to respond to incentives whether you think they should or not.

I think it's less "mindsets" that have changed so much as the incentives themselves. People no longer need to have kids in order to have sex or to have a comfortable retirement, so many simply don't. Though I'd agree there's certainly a mindset shift that has developed along with that.

There is responding to incentives and there is adopting 10 kids to farm child subsidy/benefits.