I think thats a pretty simple answer; when was the last time you interacted with a 4th dimensional object be it representation or not? For the most part I think people base their perception of reality on their experience and so if you have never interacted with something, how could you imagin it?

Reminds me of this youtube video I saw some time ago of someone that posed the question of what would minecraft be like if it was in non-euclidean space. The author said it took some time to get used to it and when they tried to play normal minecraft it gave them motion sickness.

If you have no knowledge of what a car is or its internals are like, could you still imagin what's inside?

"This argument seems like an arbitrary limitation of the human mind, which I don't think holds up. "

And why not?

Evolution did not reward us for thinking about spaced out concepts, but for coming up with new ways to get food, outsmart the prey, build tools.

That thinking in 4D is helpful for building tools is a new thing so we evolution did not optmized for it (yet).

The idea of embodied cognition might explain why we struggle to intuitively visualise objects in four-dimensional space. Basically the argument is that our visual imagination is grounded in sensorimotor systems that are optimised for three spatial dimensions. But reasoning is not limited to sensory experience so we can abstractly figure out how spatial systems in higher dimensions would work if they actually existed. Like we do for most mathematical concepts that don't easily map to what our bodies experience.

So by this perspective, it's not arbitrary, but is the result of our physical embodiment and how we interact with the world.

The only reason we can’t fly is that we don’t have wings.

It’s a limitation created by our brains evolving to process 3D environments. If we were LLMs we have no 4D training data.

A great example is the film Arrival.

People can solve a 4D Rubicks cube, so some parts are possible I guess.

Our 3D visualization relies havily on photons doing the heavy lifting of traversing 3D space in straight lines, people get, you know, accustomed to it. In fact how we see things is frozen by physics, not brains - they are just accommodated to reality

There are no such utility particles doing any heavy lifting in 4D, so nothing to accommodate to.

I can think of new colors, but I don't have a way to relate them to stimuli I've experienced, which makes it difficult to make sense of them the same way I can recall seeing existing colors. Still, I and many others have a notion of color that encompasses more than what my eyes can actually see, and I even have some friends that see much, much more in terms of color (such as texture, sensation, etc.)

Timecube... Although I'm not sure if that's what you were thinking of.

Flatland is an interesting way to think about dimensions. If we were living in a 2D world, anything living in the 3D world would blow our minds and do things we would think should be impossible.

https://en.wikipedia.org/wiki/Flatland