People like me who are excited about Jev-style models aren't going to use them to diagnose cancer. We are going to use them to make fairly straightforward decisions very quickly (300 ms or less) and very cheaply ($0.042 per M input tokens - output tokens aren't billed). Even the lower end frontier models will take much longer and be much more expensive, so these decision models are perfect for certain things.
But as the GP said, you’d likely be better off if you used an LLM to help you train a custom model to do what you’re trying to do.
If you really evaluate the best options, it’s very likely that a Jev-style decision model won’t give the best results.