[nine_k]

I tried to express the imperfection of the comparison by saying "a bit like".

Both nuclear fusion producing energy and an electric car capable of driving some distance were demonstrated long ago. At that moment, neither was economically viable compared to alternatives (both based on combustion). Both remained in that non-viable state for decades. Electric cars seem to have crossed the border of viability in certain niches; fusion power still has not.

[starbeast]

Fusion power has not yet reached ignition, without that it is not just uneconomic, it is not working period. - https://en.wikipedia.org/wiki/Fusion_energy_gain_factor