Warren Ellis is so eager and enthusiastic to show off his fantastic vistas, bizarre other worlds, spaceships, and angels - build his own high concept comicbook fantasy mythos on the vein of Sandman and Promethea and others... that he utterly neglects what is important to the story, the strength of its characters and plot. With the foundation cracking, all those imaginary dreamscapes crumble and collapse, unable to carry their own weight. It's a shame, really.
Basically it's all about an immortal superbeing saving the world with the help of his equally extraordinary friends. He's pretty much a white blood cell of the universe, set to protect the world from things that would do it harm - a pretty inventive superhero origin that could just have used a better story to carry it on. Problem is, it doesn't look like he's ever even remotely challenged in the story, isn't changed by its events, doesn't come to any big mind-bending realizations - he just breezes through everything like it wasn't there. Same thing with his accomplices. They sometimes stop to ponder, and navel-gaze, and spin yarn about the universe and their own place in it, but none of it ever actually results in any character development or growth. As a consequence I can't relate to them nor especially care what happens to them: for all its impressive action and great big gods and weirdass angels, none of the stories actually lead anywhere. They don't have adventures: in each issue they just come to a place, see something weird, spill out exposition and infodumps, then leave with no conflict.
The antagonists are completely toothless. We're always told how evil and terrible they are, what they've done to the world and what they plan for it later, but for what we're shown, whenever they do appear in the story they go down like a bunch of chumps. Two of them show up for a few pages, are hyped up some more, then get brought low without any effort whatsoever; the last two get to gloat for a while and be stereotypically villainous and irredeemable, and then down they go as well. They were never developed as characters, they never brought any new perspectives or dimensions out of the main heroes, and I never came even close to taking them as seriously as I should have.
As a consequence, what we get is a rather pretty and well-drawn world tour with no conflict, no stakes, and no substance.
At one point the main villain wonders why Snow even cares about this one little world, when there are countless others out there just yearning to be explored. Well, that's a good question - why do we care? The very beginning, the discovery of the multiverse snowflake, could have set up a vast cosmic adventure, so why didn't we get to see any of that? Why were we stuck down here doing nothing of consequence?