Let's just toss out all physics pre 2000 because it's old. lol. Truth doesn't age. Just using ITER as an example. I can update that link with a Commonwealth one in a few years I suppose.
Manufacturability is a function of a lot of things like parts, systems, interactions, size, mass, supply chain, transportability, etc. Generally speaking, more complex things are less manufacturable and they become manufacturable by simplification and reduction. As a kind of measure of manufacturability, look at the cost. Think about the most expensive piece of technology that is mass manufactured today. It's probably the 777 or 737 - so price tag on order <$100M. Big ships are on order $10Ms. Maybe military procurement goes into the $500M, but those are low quantity and generally failed programs.
So if it's more than $100M and much more complicated than a wide body aircraft, today's economy and technology level is probably not going to be able to mass manufacture it.
The size and complexity of these fusion systems is physically constrained by various factors many of which are physics limited. And even with the innovations they propose but have yet to prove out, the size and complexity is still too large to manufacture.
Regarding fusion's proliferation risk: "One of the best ways to produce material for atomic weapons would be to put common, natural uranium or thorium in the blanket of a D-T reactor, where the fusion neu- trons would soon transform it to weapons- grade material. And tritium, an unavoidable product of the reactor; is used in some hydro- gen bombs. In the early years, research on D-T fusion was classified precisely because it would provide a ready source of material for weapons."