Performance is part of the product

Performance gets treated like engineering hygiene because it’s convenient to measure it with engineering tools.

But the user doesn’t experience a bundle size.

They experience waiting.

They experience the interface responding immediately or feeling reluctant. They notice whether the next screen appears while their attention is still attached to the action that caused it.

That makes performance a product characteristic.

The useful question

Instead of asking only:

Is this fast enough?

I prefer:

What does this delay make the product feel like?

That question tends to lead somewhere more useful.