The method of placing text boxes actually makes sense. The general thinking is that there are two "modes". When you are typing (i.e. there is the flash i-beam), you are in "typing mode". Thus, when you place an object, it embeds it in your text, it does not float above it. When you click in the margin, however, you enter "layout mode". Now, when you place an object, it is not embedded in the text and you can move it wherever you want. The reason the text box icon is grayed out in typing mode is because why would you want to embed a text box in your text? You wouldn't, because it would be the same as typing. Thus, you must enter layout mode to do it.
This could be made simpler by Apple perhaps adding an icon in the toolbar that allows you to explicitly switch between typing and layout modes. My problem with Pages is that it is not easy to access the very basic features of a word processor. You need to be able to center text, for example, or change fonts right from the menubar (why are there buttons for subscript and superscript but not bold, italic, etc?). It's way too much of a pain to open the inspector or font window to do this.
This could be made simpler by Apple perhaps adding an icon in the toolbar that allows you to explicitly switch between typing and layout modes. My problem with Pages is that it is not easy to access the very basic features of a word processor. You need to be able to center text, for example, or change fonts right from the menubar (why are there buttons for subscript and superscript but not bold, italic, etc?). It's way too much of a pain to open the inspector or font window to do this.