Those growing up with Remote Controls of the kind: https://i.imgur.com/AIqz63k.jpg After a few days, the user develops a muscle memory of sorts. User doesn't even have to look at the controller and all actions (and feedback) are executed through the tactile interface. From cockpits to nuclear power plants to home tv remote control, there is absolutely nothing that replaces physical buttons, encoders, sliders and togg…
While agree with most of what you said, I have seen a lot of happy Face ID (over Touch ID). I think your 3 important points set a good framework for anything buttonless.
- Vintage radios with sliding marker that shows what the current station freq is - 3 state sliders that show whether something is state A/B/C by simply looking at it. When performing action on such a slider, user immediately knows by the means of performing the action, what the state of the system is! - Volume knobs, shows the current state. - Big bright ON light when a Keithley power supply is supplying power - Lots of Braun products, too many to list.
May be these are obvious but it just reminds me that things we take granted are really important in UX/UI.