Fusion was never viable. The things that NIF puts out is a pretty, sanitized excuse for general public for nuclear weapons development (not complaining about it)
Well you are correct that it never was and we still don't know if it ever will be. And even if it is tomorrow building new powerplants will take at least 30 years. Our current fossil power problem should have been solved 30 years ago!
I'm not sure how a tokomak or laser confinement reactor translates to nuclear weapons. Those are completely different processes for creating fusion reactions. A fusion bomb literally just explodes a fission bomb next to the fusion fuel to get it started. No lasers or magnetic fields required, because the fuel in that case is compressed by a carefully engineered blast wave.
I’m not sure how a [...] laser confinement reactor translates to nuclear weapons.
Well, that's your lack of imagination or domain knowledge, or both.
As it happens in current political climate, you can't just pull out a half megaton thermonuke and test it over some desert or atoll. The second best thing is simulating the entire thing as well as you can and that's what all countries that have thermonuclear weapons did after testing was banned. Probably the most open and transparent about it is France, with them stating that they did just that, complete with their own NIF-like facility.
Inertial confinement fusion experiments (which can be achieved by squeezing it with single current pulse like Z-machine or, better yet, heating with lasers like in NIF) mimic closely conditions within secondary stage of thermonuclear weapon, but it's more to it than fusion. Compression of capsule involves ablation of external layer - rapid evaporation pushes the rest of capsule inward, then hydrogen is compressed and ignites - again, not a simple process, because things happen so rapidly that there's not even a single temperature that can be ascribed to that plasma; then capsule and plasma interact - again, nothing is simple about it, because denser medium is on the outside, that means any imperfections will start turbulent mixing, something you want to avoid. Then, you can measure how materials behave under this intense 14MeV neutron and gamma pulse, something they do and something that's more useful for military purposes
You can't simulate (reasonably accurately anyway) these complex phenomena out of first principles, but you can make minuscule diorama and measure it. That's what NIF is for, with the only differences being 1. scale and 2. that NIF uses UV and real world nukes use X-rays. NIF is even located within LLNL, where about all modern american nuclear weapons are designed ffs. Straight from wikipedia headline:
The Z machine's origins can be traced to the Department of Energy needing to replicate the fusion reactions of a thermonuclear bomb in a lab environment to better understand the physics involved.
Fusion power, especially pulsed approach, is and always will remain a pipe dream and nice, palatable cover for general public, to be believed in by wide-eyed idealists and people who confused B-class sci-fi with documentaries. The value of collecting all that critical data for simulations, is just too great, and it's something that you can't obtain in any other way. Well, at least if you want to have functional diplomacy.
And it's not like that I'm against development of nuclear weapons, I'd just appreciate some clarity and honesty in this topic
Here's the summary for the wikipedia article you mentioned in your comment:
Stockpile stewardship refers to the United States program of reliability testing and maintenance of its nuclear weapons without the use of nuclear testing.
Because no new nuclear weapons have been developed by the United States since 1992, even its youngest weapons are at least 31 years old (as of 2024). Aging weapons can fail or act unpredictably in a number of ways: the high explosives that compress their fissile material can chemically degrade, their electronic components can suffer from decay, their radioactive plutonium/uranium cores are potentially unreliable, and the isotopes used by thermonuclear weapons may be chemically unstable as well. Since the United States has also not tested nuclear weapons since 1992, this leaves the task of its stockpile maintenance resting on the use of simulations (using non-nuclear explosives tests and supercomputers, among other methods) and applications of scientific knowledge about physics and chemistry to the specific problems of weapons aging (the latter method is what is meant when various agencies refer to their work as "science-based"). It also involves the manufacture of additional plutonium "pits" to replace ones of unknown quality, and finding other methods to increase the lifespan of existing warheads and maintain a credible nuclear deterrent.
Most work for stockpile stewardship is undertaken at United States Department of Energy national laboratories, mostly at Los Alamos National Laboratory, Sandia National Laboratories, Lawrence Livermore National Laboratory, the Nevada Test Site, and Department of Energy productions facilities, which employ around 27,500 personnel and cost billions of dollars per year to operate.