Flaky tests don't cost you in CI minutes. They cost you in developer trust. And the compounding interest on lost trust is the most expensive tax in engineering.
The Cohn test pyramid has been gospel since 2009. It was a useful heuristic for a 2009 monolith Java app. It's been quoted unchanged ever since — and most modern stacks don't fit its shape.
The 40-page IEEE 829 test plan: written once at kickoff, opened twice during the project, abandoned after release. There's a single-page replacement that teams actually update.
What automation replaced was regression checks — running the same path repeatedly. What it didn't replace, and can't replace, is human intuition trying to break a product.