There is most certainly still prompt engineering involved. How there can be both the responsivity to different cues like "plan this", "write this", "analyze this", "defend this", "poke holes in this", but not responsivity to the various terminology you provide in your explanations of "this", where to get information about specs/standards/requirements, what details I care about, and therefore can't compromise on, vs what details I'm willing to accept whatever the top reddit post from 4 years ago recommends.
I don't see how these systems can have the ability to be effectively expressive about all of the minutia, and not have all of the various different possible expressions lead to vastly different outcomes.
I think all of the cues that you just described are in the plan.
For example - I might (real world example from this morning):
"Create a script that installs hashicorp vault and consul, store the data on consul. Then create ahelper script that will fill the vault server with sample data. Add HTTPS support. Now write a framework that reads and decrypts the encrypted data in consul. Support old (pre 1.3) and new (post 1.3 vault). "
That generates a 6 page plan using Opus 4.8 w/1mm context, including notes on what to prioritize, what format to create the scripts in, etc... (My cursor guidance already has a couple months of hints as to what I want in terms of scaffolding unit tests, canonical linux, performance, security, etc...)
That 6 page plan is the "Prompt" - but it's entirely generated by Cursor/Opus. It's there to tweak if you want to emphasize, or provide some taste - but, honestly - it probably does a better job than I would - so ~90% of the time I just accept the plan as is.