The challenge with toolkits confined to <canvas> rendering is their inability to effectively utilize the browser's integration with the OS. Key components like

The challenge with toolkits confined to <canvas> rendering is their inability to effectively utilize the browser's integration with the OS. Key components like font rendering, input methods (including standard key shortcuts and behavior within input fields), selection handling, image decoding, network stack, native-like scrolling, and accessibility features need to be recreated from scratch. A web toolkit must use the DOM for optimal performance. (and therefore lower to HTML)