Apart from being uncharitable, that's just not a reasonable generalisation of human behaviour. Plenty of old people with no relatives have died wealthy wile living very simple lives, giving their wealth to charity. Wealthy retirees with lots of relatives have left all their money to their cat, or whatever. It's just not possible to paint big swathes of humanity with a single broad brush.
I’m not intending to be uncharitable - I agree that there are plenty of people of all sorts. My point is that there will be some people who really don’t care - these could be younger or older, childless or whatever. I am not sure if there is going to be much more than anecdotal evidence on who causes the most damage to the environment and who is likely to change their behaviour due to climate change.
I’m also not saying anybody would be wrong to not care about the future. It’s quite understandable to me someone using their freedom to say f the world, question is if everyone needs to be on board to make necessary changes then how do you achieve that.
In other words the point isn't the (admittedly unjustifiable) generalisation, it's that there are people who are not going to be on board unless they see something in it for them. Could be a wealthy childless retiree, or it could be someone in their thirties with four kids travelling round the world for work racking up air miles for their career to support their family.