By quantifying the result.
Now, you or someone else vibe-coded a new tool. You created new solutions and measure again.
You have just quantified the result of using the new tool.
But how could they possibly know what they should care about if they don't understand the code?
> how do you find out that was really the feature that should have been built next?
Phew right they don't know. Only the devs understand what software should do.