I was totally with you until "70% of things are pretty systematic and repeatable". This has not been my experience, and I think you acknowledged it yourself when you said "Google (as opposed to e.g. a bank)" - there are many more banks in the world than Googles. The main challenge will be transitioning all those "banks" to "Google's" and further still. They have 10y+ codebases written in 5 months by a single genius engineer (who later found his luck elsewhere), then hammered by multiple years of changing maintainers. That's the real "70% of things" :D