Oh yeah, context is the thing. But I believe you need to know what's going-on on architectural level.

For example If I ask LLM to build an analytics system where, there is soooo much data to ingest and LLM uses postgresql for the DB but we know ClickHouse is the great fit here, given the analytics queries we need. So, then you are right LLM can definitly figure out ClickHouse or something better, If we provide full context of what we want, but getting to know the full system and feeding LLM with the right context is something where we need understanding of the tech-stack atleast in general (might not be specific to the underline language).

I don't believe LLM can ever build a system from end-to-end reliably.