The vertical lines are always vertical, but the horizontal lines are drawn at an angle, when drawn on isometric dotted paper. You could get some isometric paper and draw the cube yourself.

The limitation of isometric drawings compared to 3D models is that you can't change your vantage point, you have to see the drawing from the top viewpoint. How to draw an isometric cube ...

ISO-CUBE Isometric 3D Drawing Tool 11:58 am July 10, 2018 By Julian Horsey ...

Isometric objects are still three- dimensional, only the horizontal lines stay parallel to one another. In a two-point perspective drawing the parallel points eventually merge into what's called a ...