Yes, UX is the key. The iPhone succeeded because they didn't just take macOS's mouse/keyboard UI and slap it under a touchscreen. They took the limitations and strengths of capacitive touch and designed a bespoke UX with new concepts everywhere.
Input modalities define platforms. Eye tracking is a new input modality and will define a new platform. It needs a whole new UX designed around its limitations and strengths. It needs a keyboard, it needs a browser, it needs copy and paste, it needs an app switcher, it needs a whole vocabulary of standard interactions and best practices. Apple has a good start in Vision Pro but they're not going to be the only ones doing UX for eye tracking. There's definitely room for other players with fresh ideas.
Another good example is the early "handwriting recognition" of Palm Pilot. They didn't try to increase the accuracy of recognizing all letters, they tried to hit the sweet spot between what they coudl reliably interpret and what users would learn/put up with.
Input modalities define platforms. Eye tracking is a new input modality and will define a new platform. It needs a whole new UX designed around its limitations and strengths. It needs a keyboard, it needs a browser, it needs copy and paste, it needs an app switcher, it needs a whole vocabulary of standard interactions and best practices. Apple has a good start in Vision Pro but they're not going to be the only ones doing UX for eye tracking. There's definitely room for other players with fresh ideas.