I've played and read my fair share of reviews for the game. I, personally, don't think the game is anything less than a 7 (barring game breaking bugs affecting your play through, of course).
The problem is that the review scale isn't the same across the board. People generally see something like a metacritic score as a school grade. Where 70 is a B, for example. In that scale, a 7 is considered average and a 5 is considered just passing, while anything below is considered a fail.
Looking at someone post Edge's review system, a 6 means competent. I can 100% see how someone can come to that conclusion playing Gears 5, especially if third person shooters aren't their thing. But this just reinforces my personal opinion that scores mean less and less as the industry moves forward (especially for games releasing on Gamepass).
And yeah no, that's not how it works. Even the 8s can still have quite a bit of thought behind them.
Edit: and it turns out that review scale was dropped? Either way, Most (or at least a hell of a lot) of people see the reveiw score as the grading system, not a full scale out of 10. That's also why converting a 5 scale to 10 scale directly doesn't really work. A 3/5 isn't a 6/10.