To sum up the article, because it looks like people are getting the wrong idea.
1. One of the chief ideas behind locking up Ibaka and not Harden this summer was because it's better to have a core of two wings and a big than three wings.
2. The difference between the Thunder being future champions and not is Ibaka improving as a player. He has to play at a borderline all-Star level for the Thunder to succeed.
3. Ibaka's a good defender, but his weakness is that he helps "too much" on defense, often leaving passing lanes open for wide open shooters behind the 3 point line, or giving opposing players (ie. Lebron) a path to attacking the basket. THAT'S what killed them in the Finals. That's a team problem too, but Ibaka learning when and where to move around would go a long way to fixing the problem.
4. He also has to be more productive in pick-and-roll situations, learning when to cut and when to pass during a hard drive to the rim.