But it's also just, well . . . I hate to say it, but it's really dull.
And that's the problem: this is a fascinating story! It's about how art is the soul of our civilization, and about how preserving a culture might be worth even dying for. In some ways, it's a deeply conservative movie: it's sure that the best of the past is worth hanging on to.
One problem might be related to The Untouchables: it's a little hard to believe these people are real. One character, played by Bonneville, is (we're told) haunted by some real demons. But everyone else is given barely more than a second to become a character. Damon's character has a moment or two where he has to make big moral choices, but we never really imagine it's much of a struggle. These are the good guys. They do the right thing.
That makes it easy and comfortable to watch, but it does render the film a bit flat, further compounded by the fact that pretty much everyone in this movie is either one of the good guys or just a good guy caught up in a situation bigger than him: a German soldier, for instance, who's just doing his job. The only truly bad dudes are Hitler (obviously) and two Nazi soldiers whose evilness is clearly indicated in large hand gestures.
A bigger problem is with the movie itself. It's trying to make a strong argument that art is as important to a civilization as anything else—perhaps the most important thing. It argues that it's important to conserve not just for its economic value, for what it's worth to collectors, but because it belongs in a sense to all of us. This movie believes in the greater good, and believes that our common good is tied up with our cultural artifacts and the stories we tell about ourselves.
Today, movies are that shared art for everyone, even as they grapple with how to remain financially viable. They're one of the last forms we have that are experienced and discussed on a broad, nation-spanning level. On some level, Clooney knows that. He keeps making historical (and historically-informed) movies that ride that dangerous line between meaningful and preachy. Sometimes he pulls it off.
But nothing about The Monuments Men would inspire someone to go into art-making or art-conserving as their life's work. It doesn't inspire belief in its premise; at best, it asserts it, in way, way too many voiceovers by Clooney. Your average art-lover (or movie-lover) gets how important art is, and might nod along.
But if you're aiming to make your audience believe something about art's vitality, then show them how important it is. Don't just let Clooney's rumbly baritone say it over shots of art.
There are some moments when the movie walks up to that line—one in particular, where some of the art is torched by Reich soldiers, made me gulp. But on the whole, it veers too far into substituting bland, broad joking, touching vignettes, and sonorous voiceovers for doing what movies do best: help us feel what's important on a gut level.