> And there's also opportunity costs.

That's not really how it works. ITER has a budget measured in billions over multiple years, the global energy industry is trillions every year. The amount needed to do the research is such a small proportion that if there is even a tiny possibility that it could long-term provide a significant proportion of world energy, it's well worth doing the research. The scientific knowledge gain is just icing on the cake.

> That's a lot of time for the world to get worse while waiting for fusion to happen, and we might as well just throw renewables at the problem now instead of waiting.

We can do two things at once.