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What is Silman actually trying to say here? That it requires tremendous work to take the isolated pawn? That the formula is complex? That it is not possible(unless the opponent does not bother defending it) to take it before all these requirements are met? 
[FEN "6k1/p2q1p2/1p2p1p1/3r3p/3P3P/P1Q3P1/1P3P2/3R2K1 w - - 0 1"]
What Silman describes here is a textbook scenario of what you should be aiming for when fighting an isolani. If you reach the diagram position, you will collect the pawn and win the game.
But of course, this is not the only way to win a chess game. It should be considered as guidelines: exchanging minor pieces is good because it reduces the value of the outpost on e5, keeping at least one rook is good because it can attack and pin the isolani, and the opponent's rook is clumsy at defending, etc.
Also, it is a warning that the camp with the isolani must do something specific, building an attack or changing the pawn structure, because if the game follows a quiet flow with simple exchanges, they might find themselves trapped in this losing scenario.
What Silman is "trying to say" (actually saying,in fact) is that these are the things that you should be trying to do if your opponent lets you. Tactical struggles take place not just over the gain of material but over the control of squares or to change the Pawn structure. Between strong players much ingenuity will be devoted to such struggles and the ideal situation will seldom be achieved. Although the diagram shows an isolated Queen Pawn (IQP) Silman's general principles apply equally wherever the isolated pawn.
To be more comprehensive, the advice should include recommendations for the player with the isolated Pawn. which the opponent must aim to frustrate. Specifically with the IQP, there is often the opportunity to dissolve it with d5, which sometimes just simplifies and sometimes releases a flood of active pieces. Sometimes players prefer to remain with an IQP for sake of the attacking chances, and that takes us far from the question. Silman is certainly telling us that the matter is complex, but he is still not telling us (here) more than half the story.
I think it can be formulated even simpler: Unless the side with the isolani has a bishop that doesn't protect the pawn and the other an attacking bishop or a knight, the pawn can be protected the same number of times it can be attacked, so a direct attack is hopeless unless the pawn gets pinned on the half-open file or a defender can be kicked away. (Which essentially holds for all targets!) Since the isolani side must be very helpful to let this nightmare happen, usually the attacker uses higher mobility and/or creating a second weakness (also a standard motif not constrained to isolanis).
