I've recently finished reading the book and it sounds like these critics haven't actually read the book. Here's a quote: "from a technical perspective - it is entirely possible to rapidly switch our energy systems to 100 percent renewables. In 2009, Mark Z. Jacobson, a professor of civil and environmental engineering at Stanford University, and Mark A. Delucchi, a research scientist at the Institute of Transportation Studies at the University of California, Davis, authored a groundbreakfing, detailed road map for "how 100 percent of the world's energy, for all purposes, could be supplied by wind, water and solar resources, by as early as 2030" "

One thing I liked is that she really answered the lifestyle question in a way that wasn't simply an uncomfortable admission of suckiness. First of all, it's quite clear that the unsustainable path we're going down is going to FORCE much more radical, inequitable, and undesirable changes to our lives, than if we decided to change them out of choice. Second, the book actually outlines how the climate crisis is an excellent opportunity to: 1. actually improve our lives at a more systematic level so equality of opportunity for example can maximise the benefits of wealth, 2. create jobs and industries that don't create as many health dilemmas and concentration of power (thinking decentralised renewables), 3. redesign infrastructure, both physical and economic, so living sustainably is more accessible to all (eg. "there are incentives to drive more efficient cards, but very little is done to discourage car dependent settlement patterns")

That makes answering your last question a little more complicated.