it is more like this.

Evolution = The speed of dropping a one pound stone from X height on Y place on earth without wind resistance. It is something that is fairly basic and the odds that we got it wrong is extremely small.

The theory of evolution that incompasses exactly every way it can happen, details on the molecular level and every development tree in history might change bits and pieces. But the large parts have stayed the same for a long time.

Compare this to the theory of gravitation. Sure we know the rock is falling but we know much much less why it is falling than we know about evolution. But the idea that we got the whole idea about that a rock is actually falling when you drop it wrong is pretty damn minimal, even if we don't know everything about gravitation.