ContentEditable never really specified much of a cross-platform standard API. If we wanted to replace CKEditor and its ilk, we should have pushed for a standard

ContentEditable never really specified much of a cross-platform standard API. If we wanted to replace CKEditor and its ilk, we should have pushed for a standard spec on textareas with rich structured editing support for a variety of formats (Markdown, reStructuredText, HTML, etc.) But that would then require standardizing structured text formats and/or figuring out how to add extensible functions, what to do with copy and paste especially from third-party apps, how should drag and drop be handled, what about saving, auto-saving, how should you add styles to a drop-down list to let users pick their own fonts, font-sizes, etc. These are complicated things to get right, often site- and implementation-specific, and contenteditable allowed for direct text manipulation and editing (with spell check and native text cursor flickering) within HTML, which is good enough to build your own rich editing interfaces around. So, it would be going too far to say ContentEditable was supposed to put these RTEs out of business. In fact, I would argue that Markdown's popularity has done more to put RTEs out of business recently, and that block-based, template- or widget-integrated text editing is the future, and where these tools' APIs are headed.