Thinking about it some more, it comes down to editing...
- Digitization is pretty much solved
- digital mixing is pretty much solved
- storing multitrack is trivial on modern SSD's
But editing workflow is not. It is true that for most uses, any DAW of the last 10 years or maybe 15 would be more than adequate. It is also true that the last 10 years have seen significant workflow improvements for professional uses like orchestral composing, spectral editing, dialog replacement, pitch correction, and so much more. Put editing into hardware and forward progress would slow considerably. Watching a professional ProTools editor at work is astonishing. Same with what happens in a film scoring Cubase template with several hundred or thousands of tracks. These would be hard to imagine in dedicated hardware.
But audio recording and editing? Something like the iz-Technologies Radar is probably close. I think you can still record and edit on that without running a DAW on it.
After 10 years of learning a complex piece of software like a DAW, would people switch to something fixed? Pro's confident in their workflow? I could see it. If there were zero crashes, zero latency, and rock solid repeatable reliability and a very human creative interface with good haptics? It sounds very desirable (and expensive).
But I have thought seriously about using my DAW as just a recorder and editing station and doing mix down through my SQ-5 digital mixer. But there are lots of genres that are dependent on automation... That still says DAW. But audio priority workflows with live musicians playing together could arguably be done better without a computer if the human factors worked. The proof is all the great albums made on tape with and without console automation. It is probably hard to put that genie back in the bottle...