The happy path for me is with erlang, due to the concurrency model the blast radius of an error is exceptionally small, so the programming style is to let things crash if they go wrong. So, really you are writing the happy path code only (most of the time). Combine this approach with some very robust tests (does this thing pass the tests / behave how we need it to?) then you’re close to the point of not really caring about the implementation at all.
Of course, i still do, but i could see not caring being possible down the road with such architectures..