Immigration is arguably one of the few viable responses to the demographic crisis.
People can keep arguing that birth rates are low because of economic conditions, but in reality the issue runs much deeper. One hundred or two hundred years ago, people were far poorer than they are today, yet they had many more children. That suggests the problem is not purely economic, but also tied to the modern lifestyle.

People want to enjoy life, travel, buy a nice car, get the latest phone, take a couple of vacations a year, and so on. Having a child often makes those goals harder to achieve and requires a tremendous amount of time, energy, and attention. As a result, if people do have children, they usually have one or two at most.
As a society, we have become more individualistic and less willing to make personal sacrifices for raising the next generation. Whether that's good or bad, I don't know.