The dead end is the design, not the concept. Tokamaks have been the primary focus of fusion research for so long because the Soviets claimed some success with them in the 60s. As it turns out, the claimed performance doesn't scale even remotely, which became obvious within just a few years, but the initial performance gains caused everyone to concentrate on tokamaks, to the exclusion of everything else, far longer than was warranted. We've subsequently had 50 years of research on tokamaks with very little to show for it, with other promising technologies getting short shrift, or being ignored entirely.