The problem is that ITER is funded as a science project, and the researchers want to get as much research as possible.

So they are going to spend a lot of time studying plasma before they irradiate the vessel with fusion byproducts and it's no longer safe to take apart (for example, to add new sensors).

It's the only facility of this size so the research program is completely sequential.

We could have fusion, we just need to spend $20 billion a year for 10 years. Not $1 billion a year for 200 years.