The difference between Civ4's combination of exploits was that none of them, nor all of them in tandem, were as game-breaking as ICS. Civ4's exploits never singly won games. Having a Globe Theatre draft city was powerful, but it never conquered the world. Whipping out 6 Axemen in 4 turns was powerful, but it never conquered the world. Using Quechas to steal early Workers was powerful, but it never gave anyone crushing tech leads. Hippodrome antics are powerful, but they never gave anyone +1000 economy/turn. ICS does all of this, and more.
(And most of the nonsense going on in Civ4 only really brought the player to parity with the boosted AI...)
ICS is powerful to the point that, by not doing it, you're always making the wrong decision. The difference between ICS and traditional exploits is best described in CCG terms: traditional exploits are 2 cards that go very well together, and ICS is that 60-card deck that wins 70% of its games on the first turn and 99% by the second. You can use a deck of good 2-card combos and use them to gain a gradual victory by outplaying your opposition, or you can go for the ICS deck and play with total disregard of the actual game. Look at Sulla's France game - he chose a Diplomatic win because, at that point, the opponent's activities were totally irrelevant and he just wanted to win with minimal hassle.
That may very well be the textbook definition of broken game design.
Problem is no one at any point has proved that ICS is the best way to win. Even at deity the game is so easy there are lots of ways to abuse the system which result in a fast win without using ICS.
People keep using Sulla's game as an example of how broken ICS when he didn't even win the game that fast at all. T270 really isn't that quick.
Note I'm not saying ICS is bad or doesn't work but saying not doing it is always wrong is just rubbish.