I think you're right that the use case for an LLM is still rather niche. It's perhaps still worth exploring though as they may well improve over time.
Regardless, I have still found them useful. Diagnosing the problems with a car is maybe an esoteric example but is still useful.
For many months now I have been working through learning about and implementing a hobbyist analog computer with LLM as engineer-confidant. I already knew the basics of op-amps and analog computing but was surprised at a lot of the new things I discovered only by way of the LLM saying (for example), "Hey, here's a nice way to get your reference voltages…" and the project benefited from it (and I learned about a new chip/device/technique).
Yes, they do work well as a stand-in for the "competent technician with skill in the pertinent art and and fully aware of all prior art" (to use wording like to the patent application standard).
But it's only going to allow you to avail oneself of prior art/techniques.
Regardless, I have still found them useful. Diagnosing the problems with a car is maybe an esoteric example but is still useful.
For many months now I have been working through learning about and implementing a hobbyist analog computer with LLM as engineer-confidant. I already knew the basics of op-amps and analog computing but was surprised at a lot of the new things I discovered only by way of the LLM saying (for example), "Hey, here's a nice way to get your reference voltages…" and the project benefited from it (and I learned about a new chip/device/technique).