But compare it to "First commercial perpetum mobile power station will start construction between 2050 and 2060" or "First FTL spaceship will be launched in 2050s".
My impression is that if humanity had focused on the question and not the politics we would already have fusion capacity.
But do not forget, we still do not know if it is financial benefit to use fusion in the future.
https://upload.wikimedia.org/wikipedia/commons/a/ab/U.S._his...
One can turn this around and say that fusion not getting the funding in that chart is evidence it was not seen as a promising place to invest. One cannot simply presume it's a good investment and ignore any evidence to the contrary.
That's a completely inaccurate comparison - perpetual motion and faster-than-light violate fundamental physical laws as we understand them. Net-positive power from fusion is fully within the laws of physics – we've got an example in the daytime sky, and trillions in the nighttime sky. The difficulties with fusion come with shrinking it to a scale that humans can build.
I understand the GP comment as saying "First commercial fusion power station construction will start 2050-2060" is different from "Perpetual motion machine construction will start in 2050-2060" or "FTL spaceship construction will start in 2050-2060" for the very reasons you gave (among others).
You read the GP as saying something different from what you are saying, but I think you are actually both saying the same thing.
Specifically, for fundamental reasons DT fusion will have much lower power density than a fission reactor, and so have to be much larger, and therefore have to be much more expensive.