without a lot of strategy.
Without any strategy or tactics, you'll lose every single game. It is
a strategy game, after all..
Admittedly, some armies require a bit more thought than others. Black Templars, World Eaters, and Necrons kind of play themselves to a greater or lesser degree-- Black Templars and World Eaters excel in close combat, and they even get themselves stuck in with only minimal direction on your part due to their rules which bring them closer to the enemy. Necrons, on the other hand, shrug off about half of their unsaved wounds (effectively, at any rate) and only have a few units to choose from, and those units have absolutely no options-- you can use Necron Warriors against any enemy unit in the game and get fairly consistent results due to how Gauss weapons work. A Necron army need only march forward in large squads and shoot, and perhaps get stuck into close combat where their We'll Be Back rolls will allow them to outlast everyone in a war of attrition.
Eldar and Dark Eldar, conversely, require a fine touch. A single mistake with a pointy-eared army, and it'll crash and burn. Orks, Space Marines and Chaos Space Marines of the standard varieties, Imperial Guard, and Tau are more middle of the road as far as how forgiving they are tactically.