Background: I've been a web developer since 1994 and have tried multiple visual editors from the beginning. And try to keep an open mind about new ones. But have yet to be impressed by the final outcome.
What you see is all that you get with a WYSIWYG. You can design and move things around for a template, then build a website from that template(s). But when it comes to redesigning, adding functionality, or updating the website that was built entirely with a visual editor, things get messy very quickly. A visual editor doesn't know what the developer is building and for what purpose, so it attempts to work around the browser quirks in a redundant manner. This leads to extra JS and CSS libraries, snippets, and junk that isn't always necessary. For a secondary developer, all of this extra junk becomes confusing and will cause major headaches.
Am I completely opposed to visual editors? No, but it is essential for any designer/developer to learn the mark-up first. Then, if it's essential for a specific project to learn how to use a WYSIWYG editor. But to always maintain a vigilant eye on what mark-up is being dumped on the pages.