I guess here are some high-level observations I have made (for receipts, one can attempt to trace some of my replies to related threads):
Certain posters have a specific axe to grind with particular providers and will go out of their way to list out everything bad about the provider, sometimes with receipts to reviews submitted or indicating that they no longer submit reviews because they do not believe in them (or the platforms delete their reviews).
Certain posters project their activities onto the providers within the forum posts. I observed a few where posters would indicate that multiple providers that I know would be unresponsive or flake on them, when after speaking with said providers, they would confirm or show me receipts that either the poster never even made contact or if they made contact would actually be the ones consistently flaking on the providers in multiple occasions.
If I only met and interacted with the provider once, I typically just keep quiet or at the most reply back in the forum how my experience was generally or if I would or would not recommend. However, if I have gotten to know the provider or are friends with them, I am more likely to defend them here.
Perhaps @rvwnsd and @HotWhiteThirties have a point that maybe these scenarios happen far and few between compared to other times, or maybe the providers that actively contribute to the forum are not the targets of such negative publicity here. Maybe this review DB being finalized aligned with the platform will help solve for the potentially unsubstantiated, negative feedback that some providers get from time to time.