For a question in the form of:
Is XYZ effective in achieving goal ABC?
Is it valid to post an answer in the form of:
This authoritative source lists N mechanisms (M1,... MN) for achieving goal ABC.
Since XYZ does not employ one of those N mechanisms, XYZ is not effective
The specific properties of such an answer that I'd like to highlight are that
The answer does NOT contain any link to research explicitly testing the efficacy of XYZ
The answer nowhere sites that the list of N Mechanisms is 100% exhaustive, basically relying on the logic of "If another mechanism M100 was effective, that authoritative source would have listed it. Absence from a listing is therefore enough to assume the list is exhaustive".
The cited authoritative source does not contain any proof that their list is 100% exhaustive (or even a claim that it is in the first place).
The authoritative source does NOT discuss XYZ specifically as not being effective.