Every color has different things it's good at, and the best decks are usually either super-aggressive mono colored decks that don't need to do anything besides play cheap creatures and attack, or multicolored decks that combine the strengths of several colors.
You're correct in assessing that blue's primary strength is card draw, and that its primary weakness is its inability to kill creatures. But what if you made a deck with blue and black, or blue and white? You could use blue draw spells to get ahead of your opponent in cards, and then trade your cards one for one with your opponent using black or white's removal spells like
Doom Blade or
Journey to Nowhere and take advantage of your creature-light strategy with sweepers like
Wrath of God or
Languish. These sorts of decks that primarily focus on answering what the opponent is doing while getting slowly ahead in cards are called control decks, and they usually (but not always) involve blue for its card draw and countermagic. Blue also offers the ability to counter spells, which combines nicely with other colors, since countermagic can answer instants and sorceries that they can't, and removal spells can answer things already on the battlefield which blue can't.