As long as you either have many tens of millions, or you don't care about electricity, water, food, and you're extremely physically isolated and/or hidden very well and armed to the teeth, it shouldn't affect you much.

For the rest of us it's something to worry about. Infrastructure needs a lot of trained people to operate. Once the train gets going it doesn't stop, and that means as time goes on it gets worse and worse until it reaches a point of stability some X years after collapse. And you won't be able to freely and adaquetely hunt/pick your food if you're anywhere near a city until point X, because everyone else will be doing the same. Also some idiots will be bathing in the only still good stream near you with whatever leftover chemicals they can find.

Your country can open the immigration floodgates and become a country without borders (i.e. become whatever country is currently your neighbor) but that comes with similar problems listed above.

So as you can see, it's not an issue for a small privileged few. For the rest of us, its a big fucking deal. I would encourage you to look into it.

Not really, it's a matter of replacement. Plus we need a lot more people if we're going to become a multi-planet species for survival. Nothing to do really with capitalism.