You know how numbers work?
https://www.worldometers.info/world-population/japan-population/#google_vignette
They are right now 5 millions less than in approx. 2009 when they peaked (128 million). You already hear stories about villages or small towns being completely abandoned since everyone either moved or died.
In 2050 - 25 years from now - they are forecasted to be at 105 million, which is 18 million less than right now, and with a median age of 52 years. As mentioned in my previous post - queues to the doctor will get longer, thrash will be taken out less often, roads, buildings, etc. will be repaired less often and as a result with degrade more, etc., etc.
In Europe you have additional problem nobody is talking about since it's a political suicide - less working people and more retirees means more money spent on retirement pensions. So you have two choices:
1. You are going to tax people professionally active more - good luck with that
2. You are going to pay less retirement money (that is usually defined as % of your last pay check before retirement) - already the forecast for Poland in 20-30 years is your retirement being approx. 20% of what you earned just before your retirement ; if you didn't save on your own (and most people do not) you are fucked
If you were working behind the desk or in a liberal profession - maybe you can keep on working, maybe even some people still want to continue working as a means to keep active and engaged. But that will not be an option for vast majority of people, especially since government is really not pushing on making sure people stay healthy as their age.