Editors in particular, are worse for some people if they can't render Unicode text properly, have poorer rendering of fonts, can't be analysed by assistive tools such as screen readers and braille displays, and don't interact with OS and tools outside the browser the same way as HTML and native elements.

Sometimes a good compromise is to use canvas for rendering some things things on a page (the way Google Sheets does), but create HTML elements on top as needed for particular behaviour.