Why is this a question? I've begun wondering this as of late because I honestly don't think playing aggressively from the start is a good idea. Having tried it myself and finding that it fails more than 6 times out of 10, which makes it a very, very, very unreliable plan of attack.
This isn't so much "kills don't win games" so much as it relates to the fact that it utterly boggles my mind that after so many games, players still seem to lack the foresight of what's to come if they don't start out passive and work their way up towards aggressive and only when and where the opportunity to do so presents itself.
And those moments will come as long as players are patient enough. The key is to have patience, in my opinion. It may not make for that exciting flash bulb big plays games you remember fondly (of which they are generally few and far in between), but I find that it does increase the success rate of teams who, as a whole, simply choose to wait and use cunning and planning and coordination to bait, lure, and trap their opponents as opposed to a flash ignite turret dive with ult that almost always lands the enemy a kill or more.