The taxes pay for the healthcare and childcare of course, so even with those benefits if people are still not having kids, it's not the economy but the fact that people simply don't want to.
Source: lived in Denmark as an expat and had a kid while there.
It is common misconception that you pay > 50% tax in DK. It is progressive % just like many other countries. You end up paying high percentages only on the pay that exceeds the average pay scales. Taxes, are still higher, but consider that you get a well educated society(education is free, and you even get paid to go to university), you get a society where healthcare is high quality and free, you don’t see people in the street because they got sick.. and many many more. Having a child is so heavily incentivised in all the right ways. Example(day care for your child is right and not a privilege, and the government subsidises the cost). The social system around families help even setting up a Facebook group of willing parents in your neighbourhood that happen to have similar age group kids. Kids welfare are put to the highest standards.
Just writing here to help people overcome false assumptions.