If I ever got a 5 in school I was sure less than "ok" in the teacher's eyes so no...that graph sucks ass,anything bellow a 6 is garbage material with a 6 being mediocre as fuck,7 is a good game,8 great,9 amazing and 10 is a masterpiece.
The reason we rarely see scores below 7 is that gaming is pretty great in general and there are alot of systems to take into account when reviewing a game,like maybe the story is a 4/10 but if the gameplay is addicting enough it could end up as a 7/10 game in the end,its not like with movies where if the story sucks or isnt engaging that's kind of it....but then again I wouldn't trust reviewers these days if my life depended on it.
People need to start trusting their own eyes and tastes more than what some guy on the internet said about a game you have interest in.
There are plenty of 5 or 6/10 games that I love and some 9/10 games that I despise. So trust in your own instincts,they usually are right.