Explanation

You can make a useful metaphor by comparing a quantum computer to a historian.

It’s bloody hard to get data in to the head of a historian – digging, digging, digging. Once the data is in there though, your historian readily (facilely, even) fabricates a solution. But it can only be published in an academic journal read by no one.

All up, your historian is only moderately useful at predicting the past. And your hypothetical quantum computer is only moderately useful for solving current problems.