> probably not create a single component of a complex distributed system that will fit into an existing architecture, with exactly the correct behaviour based on some obscure domain knowledge that pretty much exists only in your company.

An LLM is not a principal engineer. It is a tool. If you try to use it to autonomously create complex systems, you are going to have a bad time. All of the respectable people hyping AI for coding are pretty clear that they have to direct it to get good results in custom domains or complex projects.

A principal engineer would also fail if you asked them to develop a component for your proprietary system with no information, but a principal engineer would be able to so their own deep discovery and design if they have the time and resources to do so. An AI needs you to do some of that.