I don't think it's like saying that. In most cases the point is there is no amount of effort that an individual (or even a small group) can make that would solve the problem. I'm not saying I agree with that reasoning, but it is very different to saying our kids aren't worth the effort. Like if a child was sick, a parent might genuinely believe that they would chop their arm off to save them, but they don't because it won't actually fix anything.

I think very few people (1) believe that climate change is a real and existential threat; and (2) believe that their actions can stop climate change; but (3) decide it's not worth taking those actions.