That is because you have Textwrap on the Textbox as I explained. Just turn it off in:
Sidebar > Arrange > Textwrap > None
You don't need a Textbox either. Clicking in any shape also adds text to that object as I demonstrated.
No App is really "intuitive", you always need to know something, and there are catches as well. Pages automatically applies Textwrap to all new objects and you can't have that off by default in Pages 5 and 6. In Pages '09 you can change the default and also have a style that has it turned off. The best you can do in Pages 5 & 6 is turn it off one object, then duplicate that.
Indesign really annoyed me, still does, having come from Quark Xpress, particularly with the weird way it works with Master Pages and its relatively badly organised keyboard shortcuts. But Pagemaker/Indesign users hate Quark Xpress. It all comes down to how you think and there is a sharp divide between the two approaches. I prefer logical, and discoverable.
Pages '09 has one of the best examples of top down to detail UI interfaces of any App ever. Once you understand that it is pretty easy sailing. Pages 5 & 6 are far less well organised and have a UI that wastes huge amounts of your precious screen space.
The one thing I do love Pages 6.3.1 for is the snap to align which is absolutely the best ever. Beats the pants off Adobe's inaccurate, unreliable and perpetually annoying efforts. I actually do logo and graphic construction in Pages, even though it isn't designed for it, for that one reason. I prefer it over Illustrator and Affinity Designer.