It (foreknowledge) is there when looking for it.
Stopping this massacre was the job of the FBI, which is now under fire for NOT preventing Cruz from playing out the events (why were they not able to research and find Nikolas Cruz? Was someone instructed NOT to investigate?)
The events playing out did reveal a LOT more than stopping the events would have. No one can stop the destined date of death for another, so the "blame Q for not stopping this" argument dies there.
All & all, Future did prove past here, when looking for it.