If people don't want others to be Doomers, why arent they doing something about all the doom in the world?

It's a great question.

It's best to start with zero hope in humanity if you're looking for answers for that.

Here's a figure to wrap your head around:

From this paper: Characteristic processes of human evolution caused the Anthropocene and may obstruct its global solutions https://royalsocietypublishing.org/doi/10.1098/rstb.2022.0259