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.
But you're suggesting what I already alluded to as a reason for doubting that economic fusion power will ever happen - he's the type of person who would be pursuing fusion if it seemed feasible. It's not that he's the only one, or that he knows about nuclear physics, but it's the sort of risk he would plausibly take if he didn't know of a good reason why it can't be done. Also, of course, you need power for Mars bases.
https://qz.com/1244768/why-are-electric-cars-so-much-harder-...
Tesla's continual hitting of projected targets is much more impressive to me.
You're generally right though: the maturity, risk, and timelines of fusion are much greater than either of these. Better suited to long-term gov't/military spending.
But the general principle applies. Everything is measurable and can be modeled with a predictive distribution. The more unknowns, the more variable the distribution is.
We will have energy needs orders of magnitudes more than we do right now within the next 20 years. I'm all for solar, but fusion will be necessary just in terms of dealing with climate change and the energy needs that alone will bring with it. Carbon sequestration, water desalination, etc... are all going to need serious energy behind them and will be knocking on humanity's door before the 2050s.
https://www.energy.gov/ne/articles/5-fast-facts-about-spent-...
From the article: "the U.S. has produced roughly 83,000 metrics tons of used fuel since the 1950s—and all of it could fit on a single football field at a depth of less than 10 yards."
I'd be more comfortable with a nuclear waste storage facility in my area than I would be with a coal power plant polluting the same given area.