And then you go to the arxiv paper for ARC and learn: the power density is 40x worse than a PWR primary reactor vessel, and their projected cost is $29/W(e) (vs. < $1/W(e) for PV). Also, the vacuum vessel likely wouldn't survive a disruption (although maybe they've fixed that in the years since).

Compact high field tokamaks have better power density that ITER or DEMO would, but they still are very inferior to fission reactors. And fission reactors are far out of the running economically.