There's now at least a dozen feasible and diverse fusion projects out there. So planners who assume there won't be fusion soon are obliged to explain why they must all fail.
As much as I support funding this research, "because decades have passed with little evidence of success" sounds like a good reason for a skepticism to me.
It's a (normalised for 2012 dollars) chart from a study comissioned by the US government in 1976 to determine how much money would need to be invested per annum in order to achieve viable fusion power by specific dates. You can read the whole thing here (including the unmodified chart):
The chart I have linked you includes an extra line of data not found in the original report, namely how much has actually been invested.
Ongoing funding of fusion research dropped quickly to a half and then about a sixth of what the US government knew was needed to achieve their goal. It is in no way the fault of the fusion research community that we do not yet have a working reactor, they've been viscously strangled by bean-counters for 40 years.
Frankly, I think it's a testament to the great work of some badly under-appreciated people that we're as far along the road as we are, and if you want to support funding you totally should because we've known for 40 years that increased funding is all that's holding this back.
And despite that, the fusion triple product, which has to get above a certain threshold to achieve net power, advanced exponentially from 1970 to 2000, and in 1999 a reactor in Japan got results with deuterium fuel that would have exceeded breakeven had they been using D-T.
Then governments decided to put most of the fusion money in a three-decade construction project in France, cancelled a bunch of projects, and progress slowed.
At least private investors are starting to pitch in; Tri Alpha just got $500 million, General Fusion has a fair amount, and YCombinator invested a little in Helion.
The parent post wasn't making a statement about why planners should be funding the smaller projects, they were making a statement about planners who were ignoring fusion of any form in plans about power mixes and civil engineering 10, 20 or 30 years from now. Much like how some people criticize some departments of transportation for not addressing driverless cars/transit in a plan stretching out til 2025, say.
