How is having children a fundamental right? It's a hobby. In fact, in this case I'd consider it worse than many other hobbies because you are making another person, statistically speaking, suffer because you want to have a pet project that you cannot afford.

You're just making things up. Once that child grows up it's no longer a "pet project" and contributes to the continued existence of society. Spending resources on the child is an investment into the future productivity of that child when it enters the workforce. The idea that such a logical investment is considered uneconomical is a fatal flaw in modern society.

When you consider that the type of family (highly educated) that can actually afford to have children is deciding against having children then your proposal to consider every child as a hobby is just plain stupid. Who's going to have children then? Not the upper class? not the middle class? Not the poor? Nobody?

Well, if we are talking about poverty and inequality, the child may be a net negative for society, even on the ongoing basis before you consider the initial investment.

Plenty of people are still going to have children, anyway; if we at some point find ourselves short of children, we can bring the incentives back (or just have more immigration). But I don't think it's likely to happen over the long term... the days of needing to make the maximum number of factory workers and cannot fodder for the motherland are over, at least for a time. Having children is totally a hobby.

Oh yes, lets get back to discussing eugenics instead of discussing our slow descent back into feudalism which creates such issues in the first place. This discussion has already made good progress 100 years ago. Then something happened and suddenly stopped it. Don't remember what it was...

What the heck does this have to do with eugenics or feudalism? If you want to practice horse archery, all power to you, but you better find the money to pay for it. It's inane to claim the right to be a horse archer with government support, or blame the lack of means for a good warhorse on increasing inequality. Now, if the government/society at large feels our light cavalry reserve is critically low given all the Canadian heavy infantry, it would be a-ok for the society to subsidize aspiring horse archers to a necessary extent. Then, and only then. Otherwise, you are free to pay for it yourself - all power to you!

The same exact reasoning applies to having children. I don't see any good explicit reason to produce more children across the board, in fact I see the reverse (be it global warming and the per capita emissions in the first world, the recent electoral successes based on the plight of poor workers suffering due to globalism, automation, whatever); plus there's also plenty of willing immigrants that would solve the governments/societies problem, if there even was one. So, the government has no good reason whatsoever to subsidize child-making. If someone wants to do it as a hobby, all power to them!