Originally Posted by Caprici°us
You don't get the chance to do those 1k autoattacks assuming the gold advantage between the teams are relatively even. (If your team is significantly ahead, you can afford to build whatever you want.) When your abilities are on CD, you will find yourself in the middle of an angry enemy team playing one of the squishiest non-supports in the game, like squishier than Graves. You are in no position to be autoing. Having an IE will not affect whether you will burst down their AD carry or not, if it did, it means you are underfed and they already have their defensive item, which means you will probably lose anyway.
Okay, so hypothetically: you go into a teamfight without IE and expend all of your abilities. What do you do besides run away?
Honestly you probably wouldn't even have time to run very far either assuming the enemies had any form of CC and land it on you, and considering the fact that it takes longer to run away than it does to throw an autoattack, you'd be committing suicide just by going into the fight anyway.
Of course if you take advantage of IE you're not going to be autoattacking dead center in the middle of a teamfight. You're going to find the enemy closest to you yet farthest away from the enemy pack, and then get on a side of that enemy where you have the distance advantage of being farthest away from the enemy team. If you go into the fight and blow all your abilities, and you don't have time to fight a bit after that, even with autoattacks, you picked the wrong teamfight to jump into in the first place with or without IE, because either way you're not going to get out. That's a matter of "pulling stupid moves and getting killed without positioning yourself right", not just "autoattacking with IE". Picking IE doesn't mean "stand in the middle of a teamfight and have no caution of the fact that you're risking getting focused and killed", not everybody is stupid enough to try to autoattack in a bad position in a teamfight just because they have the crit to encourage them to.
If you have something that boosts damage output at a cost, in this case mobility, you need to utilize that advantage while negating the costs. In this case it's simple positioning or not picking stupid fights and doing stupid things in said stupid fights.
tl;dr: If it's not a good idea to autoattack to crit in a teamfight, given your position, don't autoattack. Do whatever you would normally do in that case.