I do not think it can be overstated the degree to which this is -the- defining problem of the era and quite possibly the next century
A lot of countries basically are caught in a trap from which there is no escape.
1) They have a lot of old people. They need healthcare, pensions, etc. This is *incredibly* expensive.
2) More old people means less tax money, more tax burden on the increasingly few working people and families.
3) You either a) sacrifice all other public services to keep the old person money pipe flowing, b) cut benefits to old people, or c) increase immigration.
4) You get voted out because all of these are immensely unpopular.
You can try to increase productivity or growth... by this is hard, and many of the ways it can be done (like deregulation, building liberalization, and capital investment) are also expensive and politically unpopular.