I find it a little hard to put this succinctly, but basically as a dev I get a little nervous seeing all the features in the UI. In my experience any complex editor like that has to be designed around a bunch of assumptions about what kind of site you’re editing, and almost every slightly complex real world site will have aspects that break those assumptions. It could something subtle, like confusion around terminology (imagine being a non-technical editor for a book binding website, and seeing terminology about “bindings”), or features that look like they should do something but for whatever reason don’t have any effect on the components in use. The more complex the editor is, the more likely that certain things will cause confusion when they meet the real world.