Well yeah, that’s how it fits on the tag.

It's not. The walls shown here are impossible, get clipped, but the shape itself is 3D.

Don't know what you are talking about. I can perfectly comprehend it, it's a gif with moving colours.

If you look at a sheet of paper on edge, you can see a poor man's representation of one dimension, while hiding an additional dimension, made in the only way you can actually have a thing to hold with yet one more

Edit: make guillotines great again, or whatever the tesseract deems uncouth

A shadow is not the same as a line drawn by a pencil. And a 2d line can be for example the contrast of two colours, the "line" that delimits an object from your perspective - these are no drawn lines with any width, they are not there as full 3d objects. I would think a shadow is a similar case, just as a film projection. It has no thickness.