All of us can produce anecdotal evidence to show that some old people, some young people are variously wildly profligate or virtuously abstemious - especially when they are our children, but it is the generality we have to look at and the generality is that older people are more careful and younger people are more profligate in their consumption of most carbon emitting products.
I can see no good reason why young people, who are willing to put so much time and effort into protesting at COP26 or against plastics in the oceans and have often read extensively about the problem, shouldn't also have looked at themselves and how they live and how their lifestyle impinges in the problem.
Obviously none of us are perfect, but one of the great wriggle outs, you hear it a lot from non-vaxxers, as we cannot have a perfect result there is no point in doing anything at all. The vaccine does not give lifetime protection from ever getting COVID or passing it on, so there is no point in having it. We all know that is a daft attitude and exactly the same applies to not doing our best, each and everyone of us, regardless of age, to live an environmentally helpful life.