Why the artificial constraint of assuming technology is constant? In not necessarily one to hope that tech will automatically bail us out, of the growth in the previous decades has been from tech innovations like automation.
Technology has a ceiling for a given time, across the world, which is really what you're competing with in a globalized economy.
Which is to say that more technology isn't a solution out of a demographic hole, when you're competing with a country that has the same technology and better demographics.