Acquiring Serge Ibaka was always an imperfect decision. Ibaka was an ideal rather than a reality.
In some ways, he was the perfect power forward for this generation of small ball. An athletic big who can block shots at the rim and get out on the perimeter and defend guards. His presence even as late as the Western Conference Finals last year against the Golden State Warriors was game changing. He could step out and hit a jumper just as much as he could post up and finish around the basket.
That is at least the ideal.