Building defensive items should not be a newb trap
For anyone unaware, any sort of carry should usually never build any defensive item until your third item, even if you're losing, barring a few specific scenarios (i.e. Hourglass vs. Zed).
In almost every case, it's better to rush offense and hope you can either kill your opponent before they kill you, or do as much damage before you die, so your team can clean up. Building defensive items just makes you lose harder; you do no damage and often still won't survive.
This is a pretty terrible state for the game to be in, and further devolves it into 'who can kill who faster.'
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whatever.