Destiny being a blend of genres may make this worse than normal but reading this thread very very few people are even close to the actual flaws and problems the game has. And those are the people that played it.
The story is weak. The gameplay is great. The Co op is the best an fps has to offer. The loot drops are a bit sparse but not brutally so. People wanted more or expected more content and variation. These are legit criticisms.
The social aspect is janky. The only way you can make friends really is pugging strikes then friending the good players. If you already have friends the game welcomes you with open arms. That's another fair criticism.
No way is the a 7.5 game when it's contemporaries scores are taken into account. This is, imho, an industry backlash after bf4, titanfall, and watch dogs. Where they were criticized on their high scores so now the reviewers are grinding on destiny.
Sure, it's fair to you to think that. It's not exactly something we're gonna prove either way.
I'm definitely not going to agree though (especially the best co-op part). I don't think it deserves any more than 7.5 at all. Hell, I'm not sure I'd even give it that personally.