There’s a Pros/Cons table where the first row almost seems like a paradox. A “pro” of a high population density is that you have access to resources. A “con” is that the resources are still limited.
S Korea is very similar to Japan, also facing the same problem of population decline, you can view S Korea(or even Taiwan) as a lately developed and peninsula version of Japan. Each of them with limited resources and a dense population, in which made J and K what they are today (You can look up how these two countries developed, I am not an expert historian). Even China, has a significant decrease in newborn population, despite its vast landmass and less developed population.
So basically, the achievement of development is brought by whatever suppresses the population at the same time, they are sort of at the local maximum of their country at current time point. The Nordic countries meanwhile are much loosely populated, higher average resources and so on, although not as capitalist as US. Again I am not a Nordic expert, but the distinction is significant enough that I can say applying their policies in Asian countries will not work.
Each country has its own "ecology", that are of course constantly interacting with each other so to speak, but still inertial wrt some policies that are do not cope with it well.
In fact, no single one highly and densely populated developed region can have a significant positive growth in population. There is much more than just scale of economy.
I didn’t even read the pollution part. That’s a whole different topic that wasn’t being discussed.
But thanks for the downvote! Next time, please make sure your reply is up to par if you feel the need to downvote.