Before ATT happened, FB has a tool that would run experiments to assess incrementality of your advertising. It's possible, but there are a bunch of privacy trade-offs..
but the kicker is, is it better than just doing studies without the more invasive attribution data, especially in relation to the higher price and market consolidation? very unlikely. ad monopolization means more of the value in the value chain goes to the monopolist regardless of the proportion of value they provide in the chain.
Absolutely, as the controlled incrementality study is impossible without either attribution or some group-based approximation of attribution (ie. federated cohorts, etc.)
So the idea is that you run the experiment, and this can then help you understand where you should attribute value, as you know that the only difference between the two groups was the exposure to FB ads.
Now, to be fair, unless FB is most of your spend, you still have a bunch of problems, but they'll wash out equally across conditions (theoretically, at least) so the estimate should be good.