"People keep saying "the science is settled!", but when has that ever been a mantra in the scientific world before?"
Erm, all the time, actually. The whole point of science is to be able to know something about the world, and act on that knowledge. We know enough about semiconductors to build computers, for example. There's plenty we don't know about semiconductors, but we know enough to act.
The notion that all scientific knowledge is merely conjecture, based on the facts as we know them but continuously open to being disproven, and therefore not a basis for action, is rhetoric gone wrong. The openness of a piece of scientific knowlege to being disproven is not an on/off binary state. If you were to discover some facts that appeared to show that semiconductors don't in fact work the way we thought they did, and have this completely different mechanism of action, we would question whether the facts were real, and if they did ineluctably lead to that conclusion, etc etc. We'd question even harder if you told us that the facts appear to show that computers can't work at all.