> Fusion energy is really the only counterexample in history, which makes me think we are still missing some crucial physics about how it works
This is magical thinking. We know how fusion works in great detail. And “reliably triggered with minimal energy” is essentially not a thing, unless by minimal energy you mean something like 10 million times the energy of an air particle at room temperature, for every particle in a reactor.
What we’re trying to do is recreate the conditions at the core of a star - which is powered by gravity due to hundreds of thousands of Earth masses. And since we don’t have the benefit of gravity anything like that, we actually have to make our plasmas significantly hotter than the core of a star. And then contain that somehow, in a way that can be maintained over time despite how neutron radiation will compromise any material used to house it.
The reality is, we still don’t know if usable fusion power is even possible - there’s no guarantee that it is - let alone how to achieve it. The state of the art is orders of magnitude away from even being able to break even and achieve the same power out as was put into the whole system.