It's not super easy to use at first.
And it sometimes says that the basic drawing thing you want to do is off the project's scope.
But as you learn more about it and further generalize the concepts, there are often reasonable reasons for those design choices.
And the UI looks good :-)
- https://superuser.com/questions/167873/how-do-i-draw-a-box-in-gimp you need to go on a top menu to draw a rectangle