Vibe coding does not usually produce performant code, it produces spaghetti with the goal of making the user asking for work to be done to go away as soon as possible with a (often barely) working solution.

I recently vibe-translated a simple project from Javascript to C, where Javascript was producing 30fps, and the first C version produced 1 frame every 20 seconds. After some time trying to get the AI to optimize it, I arrived at 1fps from the C project. Not a win, but the AI did produce working C code.

I have no doubt that if I had done this myself (which I will do soon), with the appropriate level of care, it would have been 30fps or more.