"Measure first, discover later" can be a perfectly valid application of the scientific method. It's all about refining the resolution on reality.

The problem with dark matter/energy is that we're not guaranteed to discover anything. It might just be wrong. The neutrinos and Higgs just happened to match their initial theory, so that's a survivorship bias. We can't just assume the same will play out for dark matter. It might just be pure mathematical fiction, reflecting our ignorance and/or limitations to measurement rather than something "real" that we can zoom in on.