Are you just not understanding that the explosive growth we've experienced over the past couple centuries is not sustainable?
It depends entirely on the exploitation of finite fossil fuels. Even the most optimistic scenarios tell us that we will have to see dramatic population reductions, drastic cutbacks in consumption (both in energy and physical resources), and a general slowdown of growth. These are not things we will choose, they will simply happen as a consequence of a) running out of fossil fuels and b) getting off of them to halt the damage of climate change. If we don't do b), then a) will happen. It's really a question of whether we want to make a gradual transition to a more sustainable way of living, or hit a brick wall and have to pick up the pieces after a catastrophic collapse.
It is naive to think we will <tech> our way around this. The period of time spanning the Industrial Revolution up to now is unprecedented in human history. We don't know what will happen going forward, but it is inarguable that we are exhausting our planet's limited resources: we are destroying biodiversity, we are (perhaps irreversibly) altering the global climate, running out of fresh water sources, running out of oil, running out of phosphates, etc. etc. We do not have
the resources to continue along this path, and the impression I get from Singularity advocates is that they think we will handwave these problems away by reaching the Singularity before our energy and resource problems come to a head.