A simple point that address a lot of that is just that bad games usually get fewer reviews. There are still plenty of 6/10 and below games getting reviewed, but

A simple point that address a lot of that is just that bad games usually get fewer reviews. There are still plenty of 6/10 and below games getting reviewed, but (contrary to the idiom) you can often accurately get a decent gauge of media ahead of time. People want to experience good media, and so better media tends to have a gravity of critic and audience attention. Most reviews don't go below 7 because reviewers are people who, just like the rest of us, want to enjoy good media. A couple examples: Lord of the Rings Gollum (a recent, high-profile, but poorly received game) has 36 critic reviews on metacritic for an average of 39, Forspoken (another similarly high-profile and poorly-received game) has 7 for an average of 63, and Tears of the Kingdom has 139 for an average of 96. Someone with more free time and motivation could pull a better spread of data to really show how the two data points relate, but I'd be shocked if there weren't a strong correlation between score and review count almost across the board.