Can we add a finding to a paper which is known by other communities but not ours?
Taking an approach to one problem and translating it to another problem is a valid scientific contribution and can be a considerable creative achievement.
I know a handful of important papers that essentially do this.
If you actually achieved an improvement and it was a very obvious thing to do, why didn’t people do it before?

As you have already noted, the crucial point is how you sell your insight.
The first step is to identify the level on which you actually solved an unsolved problem (in a broad sense that captures performance boosts).
For example, you may not have developed a new method to track the movement of fast-moving objects, but you have found a new approach to study the movement of arrows by translating established techniques for studying the movement of sparrows.
This should be the leitmotif of your paper (or the respective part thereof).
Also, do not forget to cite previous studies which could have been improved by your insight.

The only thing that probably nobody cares about is your reverse engineering (unless you developed some new reverse-engineering methodologies or similar).
But as a scientist you are in company when spending a considerable amount of time on something that you could have achieved easier.
Science always looks simpler when it’s finished and nicely wrapped.