A Boring Dystopia

It's not that. We can already feed everyone in the world, it's just not profitable to do so.

And the above comic doesn't show overpopulation. It shows a terrible urbanization and surburbanization scheme. There's a lot of things we could mandate to make it better.

1. Underground telephone and power lines. Also prevents outages during storms. Gets rid of a lot of the upper noise.
2. Better lights. Prevents light pollution by having most light go downward.
3. Structure cities and town centers around walking. This means fewer roads and parking lots and more restaurants and stores.
4. Increase public transport. #3 means everyone will drive TO the city then walk. This will prevent the driving to.
5. More green spaces. Within cities and towns there should be a lot more vegetation. Corner green spaces, rooftop gardens, parks, etc.
6. Denser housing in cities. This means people can go up instead of out. Prevents urban sprawl and keeps city neighborhoods walkable.

There's probably a lot more but a big problem with American design is that it was almost all co-opted by the automobile industry 100-150 years ago. We used to have public transport within and to cities. But their lobbying created mostly sprawling suburban hellscapes like you see above. And all the rich people live in beautifully manicured neighborhoods so they care nothing for how it looks.

How do you practically impose this policy?

Why not invest in education? There is a pretty strong correlation between birth rates and education

Morally unproblematic and way easier to implement

Well you don't have to do anything, the population is going to crash in coming decades. The "survivors" will rebuild

Post-industrial civilzations are already at negative population growth, they still produce a great deal of pollution and urban bloat.

There's no magic bullet to fix the issues we face, it takes a lot of smaller solutions in addition to some bigger fixes to tie it all together. And most of all it needs to be adaptable, to allow for new fixes to be folded into the plan as a whole as it goes along.

Most importantly: it takes time. Like, lots of time. No real, effective, solution is going to make everything better immediately.

I agree, but that is sadly not viable. Developed countries already have declining natality without those measures, due to the increase of quality of life: most women and men work, they prioritize jobs, they don't have time for kids and often don't like the sacrifices that come with having them, etc. The main increase in population is in developing countries, where it would be impossible to apply those measures.

Off-world colonies are the only viable option in the long run, imo.