I strongly disagree.
Form/<input> fields are one of the areas that a native app can slaughter HTML, even if using a WebView within an app. For example, just showing the correct keyboard layout is a nightmare, and heaven help you if you need to do something slightly custom. Another example: browsers do funky shit with scrolling and zooming on input focus. Try using the best HTML code-editor from a tablet: the editing experience sucks.
Another example is swiping, where browsers like Safari Mobile (and the old Edge) decide to navigate back/forward if the user happens to swipe from the edge by mistake - killing page state. Overriding pinch-zoom for say a photo app is doable, but sometimes ends up with invalid UI states (especially if you mix in viewport sizing changes due to orientation/ua-zoom/virtual keyboard show/tab bar show).
Disclaimer: I have spent many man-months working only on making user friendly custom <input>s in HTML, and the experience blows chunks. I have developed a custom Web UI that required too many compromises in UX.
It’s literally just an attribute on the input element?
With 150 years of evolution (at current W3C standards pace) you might get an HTML spec that is capable of expressing the behavior that users expect from present-day applications. Until then we have React et al.