The actual constraint is how long people are willing to wait for results.

If the results are expected to be really good, people will wait a seriously long time.

That’s why engineers move on to the next feature as soon as the thing is working - people simply don’t care if it could be faster, as long as it’s not too slow.

It doesn’t matter what’s technically possible- in fact, a computer that works too fast might be viewed as suspicious. Taking a while to give a result is a kind of proof of work.