Whoa, that seems like a very strong claim claim and is contrary to my understanding. I know that instrumental variables can be a powerful approach, but it's not always easy to find a good instrument. And you can try to control for confounders, but it's hard to convince yourself you've gotten all of them. See, for example, https://arxiv.org/abs/1706.04692 where standard controls were of limited efficacy and it's only when they include an additional 3,700 controls that things start looking up.

Then there are things like https://en.wikipedia.org/wiki/Parameter_identification_probl... and whole books like https://en.wikipedia.org/wiki/Causality_(book) examining the problem and its' difficulty.

Can you explain what you mean?