The whole "well, not a lot of game are rated 5/10, so ~70 means bad" rationale is absolutely ridiculous logic that doesn't reflect the actual context and content of reviews at all. Yes, 5/10 means average and yes, 70s is often the lower range of review scores. That doesn't shift 70s to bad; that means that the games that reviewers do choose to play and cover are generally curated to games that at least decent and somewhat enjoyable.
Reviewers curate what they play, try not to deliberately waste their limited time. Because unlike movies and shows, there is no "so bad, it's good". And unlike movies or shows, it's not 45 minutes, 90 minutes, two hours of your life; it's 5, 10, 20, 30 hours. With those mediums, you can spend a weekend and see everything that's out - good, average, shit - and watching shitty stuff might even be fun with the right crowd or friends or some alcohol. A bad game is an isolated and individual torture for hours upon hours. No one wants to endure that willingly.
