We have a route to that direction, and have made a lot of progress. It involves ending global poverty, providing economic opportunities for women, and ensuring contraception is available.
If you have high child mortality, limited access to contraception, and few employment opportunities for women, they have a lot of children. You change that, and they choose to have fewer. It happened in Europe. It happened in North America. It happened in South America. It happened in Asia (with some draconian policies to help it along). It's starting to happen in Africa: [0] (Check the map tab to see country-by-country over time).
We can do this without draconian policies. All we have to do is work to end global poverty. People think is hopeless, but twenty-five years ago, those same people would have said there's no way we'd cut it in half by now, and we did[1].
(Obligatory plug for the Against Malaria Foundation[2], which is my charity of choice for fighting global poverty, and at the same time, climate change.)
Yeah, it’s not a practical solution in terms of implementation. However, if implemented it would work and not require Star Trek levels of innovation. There are simply too many people in the world.
Okay...but how would that work? Where are all these people? China had a one-child policy which they've recently reversed because the ratio of old people/young people has basically reversed. On the plus side it seems that with education and generally societal improvements people tend to have less children anyway. Having said that in some developed countries they're struggling with declining birth rates. Partly because of lifestyle choices and partly due to high costs of raising children...
I mentioned that it's not practical. Forced sterilization - I'm not advocating this - would do the trick. Again, it's not practical to implement just now but I think it's clear that having fewer people would be ideal and would solve lots of problems.
Good luck with that ;-)