The 80/20 rule doesn’t go away. I am an AI true believer and I appreciate how fast we can get from nothing to 80% but the last “20%” still takes 80%+ of the time.

The old rules still apply mainly.

Yes, so 80% of 100 hours is considerably less than 80% of 600 hours

In my experience, the last 20% tends to be the stuff that's less obvious, too, by it's very nature.

The details and pitfalls that are unique to your specific scenario, that you only discover by running into them.

And yet this less obvious, more uncommon stuff is also what AI will be weakest at.