This is a question of whether ergonomics will continue matter at all in the future. I would guess ergonomics will always matter. I take your point, and I even would go further to say that many GUIs don't need to exist at all. If the machine understands your goal then everything can happen invisibly. The software should disappear. However, I see these bespoke just-in-time UIs being primarily useful for one-time tasks or project-specific software that has brief utility. If the tool is being used repeatedly then it wants to conform to the user and task in a repeatable way. This is where design, engineering, and dare I say "taste", comes in. You don't want an interface to change every time you use it. Most people are not alone in their needs, and their collective need forms a market. Recurring usage is an evolutionary pressure that pushes a tool to fit the purpose and the market. The mirage of on-demand digital everything is very seductive. I saw it disappoint so many people in my industrial design and manufacturing career. There is an allure to digital manufacturing methods (like 3D printing) because you can change the output every time. But those manufacturing methods have can never compete on cost efficiency, predictability, refinement, polish. The benefits of tooling are so enormous that everyone immediately switches to those methods if the product has any scale. The critical mass is surprisingly small. Even in a world of agentic code factories where the customer may be human or agent, you will see autonomous structures align themselves around repeatable methods, predictable tooling, and ergonomically consistent interfaces. They too will have cost pressures, presumably being the support agents and supply chain operators in this world. Humans are fundamentally social, and have relatively similar needs to one another. For that reason there will always be a need for tools and objects, whether physical or virtual, that are ergonomically and evolutionarily fit to a specific cohort.
