There's no rush.

And, not to get too esoteric but... its not like you're going anywhere after you're dead. You're still in the world and of the world. As a human living in this moment, you have as much agency as anything has ever had over its environment. As an expert in environmental sciences, even more so.

I'm pouring my limited time alive into trying to help fix something that is broken beyond repair

This is fucking miserable on a global scale, but it isn't the end. No more than the catastrophes of war and plague and famine were the end going back millennia. In the same way that some British dorks fucking around doing geographic surveys in Saudi Arabia a century ago unlocked a thing they would never live long enough to comprehend, you're participating in a project you won't live to see the end of. But you're in it and what you're doing will echo through time in the same way that the actions of your predecessors did.

Leave now and all you're doing is surrendering agency to the survivors. To paraphrase Patton, don't die for your beliefs. Let the other dipshits die for theirs.