I believe Buzzfeed is an online newspaper and produces it’s own content hence the defamation action. The OP is suggesting an online platform to he used by non-associated individuals to post a review or opinion.
I’m not saying the suggested review website may never face a legal threat but i didn’t go into detail as such a scenario (or scenarios would be hugely complex and beyond me for sure.
However if a business could be reliably sued for simply providing a platform which is used by an unknown third party to produce defamatory content, then we would all be liable.
For example if the local council rents out their hall for a community meeting, and someone turns up, stands on the platform at the front of that hall to make defamatory claims about something; then surely the council can’t be sued for simply providing that platform? If they could be sued, then the builder could be sued for building the hall, the brickworks for supplying the bricks, etc etc…