However much you know about the environment you're working in, there is a way to evaluate the effects of your intervention.
What's crucial is to recognise that no one evaluation approach is better than another.
It's about picking the right evaluation approach for the stage of development of your intervention, and that is the approach that offers you the information you most need at that time.
Early stage ideas need more open data captures because you are still informing the development of your intervention and trying to understand its effects. Later stage projects should have this information, so are more interested in testing for specific impact of the work.