Anthropic and OpenAI are currently obsessed with getting humans out of the training and improvement loops. It's going to happen very soon and when it does I think we see staggering improvements in a very short space of time. Basically, the Singularity.
Try putting an LLM agent in a deterministic workflow without humans in the loop. My experience with this is not encouraging. Getting it to work requires sprinkling some context magic and hoping and praying the LLM does the right thing. More astrology or religion and less science. Great for use cases with humans-in-the-loop, but less than impressive when you need determinism and reliable operation.
I would not use a sewing machine to repair my deck :) LLMs are non-deterministic, by design.
They don't have to be though. You can give them a temperature of zero so they pick the highest-probability token every time to give you a deterministic output. I imagine this doesn't work on frontier models because there's a lot going on, but you can definitely do it with a small local model.