I am in an existential crisis all the time. But not because I want to leave a legacy. If I died and everybody had enough to eat, then I'd die happily and peacefully. But that's not how I'll die.
Someone is going to follow me because they literally starved today. Someone else is going to beat their SO to death. Someone else is going to die because they're homeless and don't have access to resources they need to survive at the very least. Someone is going to be worked to the literal bone and discarded in a corporation's supply chain. And many are going to die because fossil fuel companies are trying to maintain their profits.
Yeah, I'll be gone one day, but like...even I don't care about that. I just want other people to be able to live the kind of life I'm currently living but on their own terms. And it pisses me off and induces an existential crisis that policy ensures they don't.