Fusion is the answer to "how can we extract R&D money for decades without ever actually delivering anything." There is little prospect it's going to be competitive, particularly DT fusion. The engineering/economic obstacles are profound even if all the plasma physics problems are solved. Most of the efforts being touted are obvious nonstarters.
So, no technology is impossible? Every dream can come true? That's what I'm getting from the logic of the argument you're making there.
Sometimes technologies really do have showstoppers. There are fundamental reasons to think fusion is not going to be competitive. I know of no fundamental reason self driving cars would be impossible. The analogy doesn't work.
