"To fight climate change, we need system change"
How about turning that around.
"To justify system change, we need climate change"
Or, more accurately, we need a bogey / huge fear.
In normal circumstances your proposed radical changes will not be entertained, because they don't hold up to rational inspection; their track record is bad; they've butchered too many millions of people; they've delivered the exact opposite of what they promised (said everybody will be prosperous; ensured everyone stays impoverished).
So you need an emergency to push your agenda through.
It's all huny dory while the emergency is real.
But when it emerges to not be all it was hyped up to be, then your loyalty to your agenda overpowers your obligation to reality.
And you start down the slippery road of propaganda : of nonstop fear-mongering, of demonizing everyone who wants to rationally think about what you're advocating, who asks pesky questions. Anyone who dares to question you is to be branded away as evil. Because your cause is more important than reality.
There's another term for this. "Crisis capitalism". Ironic that it's the Left capitalizing on it.