The problem of climate change is not one of generic 'overconsumption and waste' but of bringing greenhouse gas emissions to net zero. Most of the electricity, transport and industry currently dependent on fossil fuels can be greened. There are important exceptions, like aviation, and in those cases reducing consumption would be helpful. But for the most part it's a question of substitution, not reduction.

We are also living through an ecological crisis whose causes are far more entwined with over-consumption. But that's because it has causes additional to climate change.