The entire economic premise and value case of LLMs rests on the idea that instructions need not be provided in advance, and that the model can "reason" based on evidence and "decide" what to do next.
Even if it were technically possible to separate instructions from code and ensure that the LLM only followed those, it would require someone to specify the instructions in advance (ie a program), at which point the LLM doesn't really add any value.
Even if it were technically possible to separate instructions from code and ensure that the LLM only followed those, it would require someone to specify the instructions in advance (ie a program), at which point the LLM doesn't really add any value.