Europe, compared to most regions of the world, are indeed suffering from an aging population with a low replacement rate. I don't think they're trying to be coy or deceptive. There is truth that immigration (of any kind) is meant to reverse this. Japan and South Korea fall under this umbrella. Their pension system will get destroyed when everyone is too old to work, but there's not enough young Japanese or Koreans to look after them. There is an argument to be made we could look into alternate ways to alleviate this. For example, robots could play a big role in taking care of the elderly at a reduced cost. But that all depends on how fast they can bring out that technology. Otherwise, the only solution is to import immigrations to slow down the collapse.

There's also the fact without immigration, these nations will lose their competitive edge. Capitalism and population growth are tied. If Japan or America shrink in demographics, it now means the next biggest country is closer to becoming #1. Again, the Alt-right can express disagreement for mass immigration, but understand there are scientific reasons for why it's affecting White nations that have nothing to do with a secret cabal trying to hurt them.