It's remarkable how all the races of the Mass Effect universe exhibit the same architectural proclivity for large rooms littered with small, waist-high walls. It doesn't matter if the species is reptilian or mammalian, psychic or hive-minded. All of them want to make sure their buildings include lines of crates and huge, low-slung workstations. Across the galaxy, no room is considered complete until it can provide shelter to a squad of infantry.
As much as I enjoyed Mass Effect 2, I had trouble with the repetitive environments and nearly identical battles. There were so many times where something wondrous and alien was visible in the background, separated from me by an impassable partition that marked the limits of the map. The architecture that I could not explore suggested insect hives or graceful, nonlinear spaces. It suggested soaring cities and deep caverns. But it was just background artwork. My reality was one of rectangular platforms connected by ramps, and large, open spaces dotted with cover.
Cover is the great democratizer of shooter design. With a big room, some automatic weapons, and copious cover positions, you too can create an exciting shooter! You don't need a good engine, you don't need good controls, and you don't need good weapons. Just throw some cover down, and baby, you've got a shooter going.
Just not a good one. Cover produces bland, repetitive action and unconvincing locations. Toward the end of Mass Effect 2, Shepard and her crew are supposed to be in some the strangest, eeriest places they've ever encountered. But the level design always undercuts the art. Shepard and her crew might have journeyed to the farthest reaches of the galaxy, but in a very real sense they haven't gone anywhere. It's the same shooting gallery wearing a different skin.
It's not just Mass Effect 2. One of the things that well and truly murdered my interest in Red Dead Redemption was the way every encounter followed the same script. You and your allies would run across some bad guys. Everyone would start shooting and then run to the boulders, crates, barrels, and wagons that were conveniently arranged for just this eventuality. If your character was wounded and near death, you could spend a moment behind cover getting better, and then resume the battle as if nothing had ever happened. Enemies would stay roughly in the same places, making no effort to flank, assault, or retreat. They would just pop up every few seconds, take a poorly-aimed shot, then drop back down into cover. All you needed to do was plant the cursor above their heads and wait for the next regularly-scheduled potshot. Repeat.
Ultimately I liked Mass Effect 2 a great deal, but only because I enjoyed the characters and performances so much. Red Dead didn't offer any such compensations and so I bailed on the game after the first act. But the fact remains that cover-based design made each a lesser game. It stripped away the layers of illusion. Everyone hunkers down behind bulletproof furniture and starts trading shots with enemies a few feet away. With this kind of half-hearted combat, key elements of the plot become preposterous. Mass Effect 2 steadily builds up to a "suicide mission" that grows steadily less menacing the more you blaze through opponents. The combat is so devoid of peril that it's impossible to believe for a moment that Shepard or her crew are in danger of anything worse than combat narcolepsy.
At the heart of every shooter lies a dreary reality: you drop the cursor over a target and push a button until it dies. Good shooters never let you see this to clearly, or feel like it's that simple. They force players to concentrate on other tasks. They emphasize tactics and maneuvers, or weapon characteristics. They introduce enemies designed to counter standard tactics. They change the terrain to handicap some styles of play and promote others. They keep the player from relying exclusively on the same bag of tricks.
Too often, cover excludes these techniques and actually emphasizes the repetitive, mechanical task of point-and-click combat. By its very nature, cover roots combatants in place, so movement becomes a secondary concern. Environments tend to be similar and repetitive, because they have to make room for the large, broken spaces that cover demands. Worse, these spaces telegraph not only that a fight is about to occur, but often the way in which it will occur. Not that it's hard to predict, because cover also creates exposed dead-ground between the fighting positions where nobody can survive. So fights consistently occur at medium range. This in turn makes most weapons interchangeable. Sniper rifles and shotguns become decorative accessories on a character model. They are relegated to carefully controlled situations, like the inevitable sniper sequence.
There are cover-based games I've enjoyed tremendously. Uncharted 2 comes to mind, as do the Brothers in Arms games (although cover also helped make Hell's Highway the weakest game in the series). But too often, cover is a substitute for designing a complete shooter. Instead of unpredictability and danger, we get kill-houses packed with spring-loaded targets. Cover may not cause bad shooter design, but it certainly makes mediocrity easier to achieve.