Let's assume that the engineering challenges can be overcome. Let's further assume that a Manhattan project mentality pushes for rapid development. How many decades before fusion reaches viable real-world use? How many further decades until it is available at scale throughout the world's most energy-hungry nations?

Let's be madly optimistic and guess 4 decades.

By then, our current use of fossil fuels will likely see us at a climate-devastating +2C above pre-industrial. Welcome to your billion or so new neighbours - refugees from unliveable tropical countries.

Meanwhile fusion just fuels the dangerous delusion that tech innovation will come to the rescue. I won't be banking my kids' future on that assumption.