We’re too selfish. The traits required to become a leader don’t lend themselves to solving complex long term problems. The populace wants simple solutions and to enjoy their lives as much as possible. And they will go into denial to achieve that.

In the book “Collapse” I remember it claiming that it is very rare that a society can solve such problems with a notable exception being the deforestation of Japan when the Shoguns ran the place. They had 2 essential characteristics:
1) They had absolute power (Ie it was not a democracy. Democracies won’t allow short term pain to achieve long term solutions)
2) They had a connection to their future as they “cared” about the long term survival of their clan..the future Shogun’s family of rulers.

We have none of that.