I believe the issue is that the surrounding materials of the torus in the TOKAMAK become highly radioactive due to neutron bombardment and decay accordingly.
IIRC, there is some sort of Silicon Carbon based material that need to be economically feasible to manufacture (that can withstand a fair amount of neutron bombardment without crumbling like other materials) before a plant will ever make sense. There may be alternative materials but none of them are cheap enough to build a long-term TOKAMAK even if we could achieve the incremental net power necessary for a power plant.
IIRC, there is some sort of Silicon Carbon based material that need to be economically feasible to manufacture (that can withstand a fair amount of neutron bombardment without crumbling like other materials) before a plant will ever make sense. There may be alternative materials but none of them are cheap enough to build a long-term TOKAMAK even if we could achieve the incremental net power necessary for a power plant.