Here's a question for those who say "win the game early":
How do you deal with Towers? Lane creeps won't start getting permanent stat bonuses until 7:30 so they die rather easily.
What's an "early win" ? 20? 30? What's the average level at 20min? 12?
Not to mention when you're already at T3 they hit for 122-182 have 1600 health and are (technically) surrounded by the enemy team heroes.
Key thing about dota heroes, especially compared to league if you are familiar with that game, is that dota has a far more dynamic hero power scale. In league any picked ranged AD with a full inventory performs very close to the others ads, while there is agreed upon hierarchy in league the variance between the AD's is small when compared to dota. Simple things like perhaps PL / AM / Void - these are power monsters with full slots, then maybe naix, lone druid, etc. Down to juggernaut, storm spirit, etc. This list is not meant to be comprehensive but illustrate a point.
The opposing team has an AM you have a jug? you have to win first, if the game drags on and the am isn't stupid you will eventually lose to him. In vhigh that timing might be 30/35 minutes, in normal that might be 60 minutes, but the point is if that hero gets enough farm he will dominate the end of the game. Likewise those heroes are weak early, offer generally very little damage, no teamfight, they die fast, and if you stack up your team against theirs 5v5 you should be able to calculate a relative power comparison.
Simply put, you just have to understand the idea of powercurves, for spell casting heroes that curve is generally based on level, for carries its more dependent on farm. Heroes like Shadow Shaman, Disrupter - they have extremely strong level 6s, but very weak level 1's when you stack them up against veno, juggernaut, shadow demon, leshrac etc. Winning the game early is based on an understanding of your team composition vs theirs and when your powerspike happens.
The easiest most obvious, and stupid example would to be pick any 5 melee carries, put them on a team, then put them up against leshrac disrupter lina shadowdemon and chen, now imagine a lvl 6 teamfight, or a lvl 3 teamfight, or a level 16 teamfight. There is no way the 5 carries should ever win, the only way they win is if the other team dicks around for long enough to lose to the hero scaling of the melee carries and does not go for the throat from minute 5.