The reviews are for the most part crap. That's an issue with the review process (be it the method by which it's reviewed, or the incentives that drive the review) and not an issue with the game. The game has some flaws, but they are easily overlooked by anyone who's interested in what the game is really trying to offer the player.
I'm on my first playthrough as a spy, and realistically there are very few improvements needed. I suppose my main complaint is being forced into certain gun-fights by the script. But it's a very satisfying experience overall. There's constant auto-saving to try and prevent you from re-loading saves to undo minor mistakes or re-do conversations, but imo that adds to gameplay as it doesn't let me try to micro-manage the experience.
Very few professional reviews give the consumer anything reliable. What's best is looking at the user comments below, most of the time. You get the opinion of someone who wants to play it for fun, not someone who played the game for work.