It actually is. We only perceive three of them.
You don’t perceive time? you are in another universe! ;-)
And our eyes only perceive three base colors. It's pretty hard to even imagine a new primary color. But computers have no problem imagining multi-dimensional objects and new colors. Maybe a computer generated virtual reality 5D world with dozens of base colors could be fed into a developing brain so someone could explore that kind of world and report back.
4 of them. We experience time, x, y, z and who’s to say they’re aren’t much more.
“It actually is. We only perceive three of them.”
Yes, we only PERCEIVE three, but that does NOT mean that there are not other, real dimensions, which are too small for us to even try to perceive, much less move into.