I agree, they are being way to harsh on it.  Titanfall had almost no story or co-op modes, and a multiplayer mode missing basic features like private matches a launch yet got way better scores!!

And it's not like you are paying more for Destiny either.  Destiny easily gives you 50-100 hours of fun if you really get into it, and its not like they are charging you a fee as a MMO would.

Now I'm not going to pretend that Destiny is perfect, but it is a far cry from the poor reviews it has been getting!

Here is a list of my pros. and cons for the game.

+Fun Gameplay

+Diverse enemy types

+Good loot game

+Lots of fun Co-op activities

+Imersive Universe

+seemless conection to other players

-frustrating chat system

-no private matches

-mediocre story

Exactly. I think that the reason why the rating is so messed up is because they take into consideration non-gaming elements when rating the game. One of those elements is the assumption that it cost $500m to make Destiny and therefore they should expect the holy grail of games. Another is that they compare certain elements of other games which had a smaller scope with Destiny and then say that yes, it's been done before without recognising that the game offers more than this particular feature... 

That's the thing however, I understand how people cannot buy a game blindly and then hope it's good (Bad surprises such as Aliens: colonial Marine)... however, there must be some degree of professionalism from reviewers in the sense that a game should be judged purely on gaming elements.

Because Titanfall was never hyped up as anything more than an incredible MP experience and no one was expecting anything more than an incredible MP experience. Which is exactly what was delivered, which is why it scored well. Despite, as you referenced, a lack of some pretty basic features, since the game was rushed.

Destiny wasn't rushed, and the main difference here is that at its core, Destiny just is not designed well. The good thing for Bungie is you can take a look at vanilla launch Diablo 3 and the Diablo 3 we see today and see that updates and patches can fix terrible design decisions.

Destiny is indeed far from being perfect... My personal score is 9/10 for the game based on the hours and quality of fun I've been recieving. I treat the game as an investment... the Return on my investment in terms of the hours of fun Destiny has provided me compared to other games I've paid a similar price to is 9/10. Opinions vary and I've had fun playing age of wonders 3 for example which got better reviews than Destiny and I'd still rate 8.5/10. 

On a personal level, I can understand how someone can rate the game 6 or 7/10 because it is the fun factor for them... For a professional reviewer however, who is supposed to rate the game without bias, trolling and with adequate research and analysis on the quality of the game; having a 4/10, 5/10 or 6/10 is just unacceptable.

To take an example: Gamecritics rated Destiny 45/100 but gave Wolfstein 100/100. Not to say that wolfstein, released a couple of months ago for the same price was a bad game but the difference in rating is just messed up.