First off, the people who are dismissing non-5* reviews as "70% haven't played the game" are embarrassments and need to find some integrity and look at the statistics.
I've owned an played this game excessively since launch, clocking many hours, and it's the comparison against the years of FPSs which it should be ranked against. It's not 1*, but it's just not at all a good game, for the £70 that it costs.
On multiplayer, graphics are murky in general so the players getting the most kills are blind firing at corners. The Time-to-kill (TTK) is so short it doesnt reward good movement or intelligent gameplay. The loading times are almost unbearably long compared to other FPSs and the audio is terrible.
There's basically no use for Sniper or Marksman rifles as the maps are too tightly designed, recycled and repetitive. The guns are mostly boring and don't reward experimentation, as there's few you can actually use to be competitive.
The gunsmith allows far too many attachments meaning players with a levelled up gun will pass you around like the soap in the prison showers by trying a new one. These guns are so unbalanced that leads to a strict meta unless you want to be cannon fodder.
The killstreaks are overpowered, such as the dogs (way too hard to kill, too damaging and rack up the kills for you with no input) which means even an average player (me) can hit 100+ kills a game by camping.
The campaign is short and unrealistic, the characters are downright unlikeable and a general collection of all the nationalities in a 'suicide squad'. It's so historically inaccurate I it's almost hilarious, but I won't rank it down for that since you can basically call it Sci-Fi. All in all 'meh'.
This game is basically a just reskinned MW with none of what makes it special.
The game relies heavily on appealing to the COD:World at War nostalgia, which was comparatively for the time a much better game (also a reskinned MW). WaW at least introduced the Zombies mode, which here has their worst implementation in the entire series, 0/10, a lazy and boring game mode.