It appears that the dead website that @rotmulaaginskyrim@programming.dev mentioned was not much more sophisticated than what @sub_ubi@lemmy.ml suggested, “federated reviews”.
https://web.archive.org/web/20220411192056/https://www.exitreviews.com/

Nothing is stopping you from creating a Lemmy community for general product/service reviews, but I doubt it would work very well nor be very popular. But ActivityPub-based federated reviews sounds like an intriguing idea. I don’t know if/how ActivityPub can handle structured fields (https://web.archive.org/web/20220608160103/https://www.exitreviews.com/submission), and you’d probably want a search system that leverages those fields.

federated reviews

Make a community for it? Or maybe an instance? @federatedreviews.com