Prompt engineering is a transitory phase. Embedding it into existing tools so the 80-90% of regular prompt patterns can be worked into the UI (or contextual UI designed around how a user uses the product) is the next step
Free form chat is pretty terrible. People just want the thing to (smartly) take actions. One or two buttons that do the thing, no prompting involved, is much less complicated.
There are like thousands wrappers around LLMs masquerading as AI apps for specialized usecases, but the real performance of these apps is really only bottlenecked by the LLM performance, and their UIs generally only get in the way of the direct LLM access/feedback loop.
To work with LLMs effectively you need to understand how to craft good prompts, and how to read/debug the responses.
Yeah, it often makes sense to adjust the user's prompt, add system/wrapper prompts, etc. But that's not really related to UI..