This is one of those games that need to be put in the right perspective
That means yes, the game is repetitive as all hell. It lacks a lot of things people take for granted in modern games: online modes, extra content, unlockables, varied gameplay and length clocking at 12+ hours. Also, the few things to do besides punching enemies don't seem like they're worth pursuing: for example, Rorschach can pick locks but save for a couple of instances in Part 2 where it'd lead you to a hidden Rorschach card, you won't really need to bother with the lockpicking minigame. All these factors may seem like too much to bear, especially in a licensed game.
On the other hand, all the technical aspects of the game and the core gameplay - brawling - are superb. I know few games, in any platform, with such a beautiful art direction. Level design may be too linear and inconsequential from the gameplay perspective - Zelda it most certainly isn't - but eye-candy-wise, each level is a masterpiece. The animated comic cutscenes provide a clear contrast to the generally hyperrealist setting, which is an interesting proposition. The whole game runs smoothly with no noticeable frame rate drop, and most surprinsing of all, the camera does work well most of the time (an old recurring problem both on 3rd person games and licensed ones).
But you know what's what? This game is not just a beat'em up. It's Double Dragon for the modern era - in stylish, cutting-edge 3D and under a tacked-on new theme.
In fact, all that's "lacking" in the game may have been left out on purpose. Double Dragon was a great arcade game made out of a few linear, decadent-urban levels, five or six enemy types at the most, a handful of brawling options, some weapons that can be taken from baddies or picked up on the floor, 2-player cooperative campaign and a single boss character at the end of the whole adventure - none other than the gang leader.
A description that fits The End is Nigh to a T, by the way.
If you're still not convinced, take a look at this game's trophies. There are things like "Complete the game in less than 80 minutes", "complete a whole chapter [level] without being damaged" and so on - typical arcade-y stuff, very fitting to any decent beat'em up.
Which means most of the so-so reviews may be right in a number of points, but also that they're ultimately missing the point. The End is Nigh isn't really a modern game, but a classic arcade beat'em up built on current technology, and therefore it should be played and appreciated as such. It's a game to play when you feel like punching wave after wave of clear-cut bad guys stringing as many different blows the game is capable of handling - and in a contemporary game this also means stringing combos, which is where this game shines.
If you decide to go for this - and the Complete Experience edition is a bargain, considering how good the movie is on its own - be aware of what you're taking. If you love classic beat'em ups, this is an absolute must. If not, you can still get some late rainy afternoon enjoyment if you don't expect the game to mimic current trends. It's all about the brawling and the combos, and it does it well without unnecessary distractions.