Sure, there's certainly other factors, but the US for example also has horrible working hours for the pay many people receive as just one example country, and there's no population issue there. A big part of that is the US has a large immigrant (yes, both legal and illegal border crossing) portion of the population. It's not a sole solution but it's a big part of one.
Age is important because while the population is not only shrinking, it's tilting toward the older side of the spectrum which makes the problems even worse.