So this is something that's been on my mind for awhile. Whenever I'm watching top level Zerg players the two most common reasons they lose are: 1) playing passively, 2) never teching.
Tonight the NASL aired Moman (Z) VS Incontrol (P). The first game essentially boiled down to Moman double fast expanding into a massive unit boom while Incontrol sat back and built up to his critical mass of Colossi and then swinging in for the win. I felt that this was kind of the perfect game to show my point, while Moman is no where near the most amazing Zerg ever, he's good enough that he shouldn't be making these sort of mistakes.
Early on in the game he took a near 60 supply lead given he was on 3 bases to Incontrol's 2. He punched out a ton of roaches and zerglings, and then ... stopped. Looking over at Incontrol's base he sat idly in front of his natural with a handful of units, not threatening anyone. Moman knew this, he scouted it, it was obvious he could win if he just went over and killed him and he just sat there doing nothing. What the hell? Why the passivity?
It's a universally known fact that once colossi tech hits and starts rolling the Zerg is in a seriously awful position. Roaches don't stand up to Stalkers with Colossi/Immortal support, and Hydra's with their 80hp get one shotted in droves by 3-4 Colossi.
So then the other problem creeps up, how is it that Moman is so dreadfully behind on tech? The game is in a state where Incontrol is producing Colossi, the Protoss top tier ground unit. It is the ground equivalent of a Carrier. Why isn't the Zerg now producing Broodlords or Ultralisks (preferably Broodlords, Ultralisks get kind of destroyed by Immortals and Stalkers)? Why aren't there Infestors stealing the few Colossi/Immortals that Incontrol had? I feel there's no excuse for Zerg's to get that late in the game so dreadfully behind on tech given how macro oriented the race is.
Now this game is just anecdotal obviously, but it's a consistent theme I see in top level play. The Zerg stays roach/hydra or roach/ling and never moves forward, then dies to a Colossi/Stalker/Sentry ball. This is often a result of incredibly passive play, so I feel the two kind of go hand in hand.
So Zergs, ask yourself next time the game hits 13 minutes: "Could I stop a colossus or two right now?" and the answer is no, you should watch the hell out of that replay and see why. Because that's when you'll start to see them, the average Colossus timing is between 11 and 13 minutes. I guarantee you you'll find periods of minutes where you have a vastly superior army and had you just gone and attacked them intelligently, you would win (ref: every time a Protoss 3 gate expands and a Zerg just throws ~12 roaches and 20 lings at them and wins). This will work almost every single time because Protoss build units slow as hell.