Here's something that puzzles me a bit. I'll start off with an example:

I'm playing a TAGG, i raise from the CO and i get a call from a reasonable straightforward TAGG in the SB.

Flop is AKQ rainbow, he leads out.

I raise him and bet most turns with a wide range. He folds a good amount and i win a lot of money. One of the reasons for this is because my range is much better than his range.

Now lets say the SB is ISF. The same action happens preflop and the flop comes AKQ.

he leads out. Now, he knows that he will rarely have a hand that wants to stack off here besides JT, and he knows i know this. So he decides to stack off light here to counteract this. He stacks off lightly enough to the point that my aggressiveness on this board is -EV.

So even though i assessed ranges correctly and made a good move according to those ranges i still lose. This is because ISF has out-thought me.

Which leads me to believe that Thinking >>>>> Fundamentals.

So when it comes down to it, does poker theory really matter? Because no matter what understanding of poker a person has, if someone can get in that persons head (and knows how to reasonably exploit knowing his opponents thoughts) he will always be able to outplay that person no matter how good he is at balancing his ranges or exploiting peoples tendencies (in terms of ranges).

Talk amongst yourselves... i don't really know where to go from here yet.