I completely understand this point and I think it is very valid. However, part of what makes Germany German is having a socially oriented economy. For example, having a pension system based on solidarity, without which a German custom like having a beer at the local pub could become difficult if you don't have a social net to protect you in your old age.
Now the question is: can this work without immigrants? If Germany's population shrinks, you can also kiss the culture goodbye.
Now the question is: can this work without immigrants? If Germany's population shrinks, you can also kiss the culture goodbye.