>What's more, it's a step that I don't think can be outsourced to someone else, which is why I'm skeptical about claims by, among others, the Effective Altruism movement, to be able to do this kind of thing on your behalf.

Why can't this be done? Society in general outsources due diligence to third parties all the time. Banks outsource credit worthiness assessments to credit bureaus. Passive investors outsource price discovery to other market participants. Online shoppers outsource quality control to reviewers. I agree that there's no substitute for doing it yourself, but it's simply not realistic in many cases to do the due diligence yourself. Even if you do it yourself, there's no guarantee that you'll do a better job than the professionals.