Draw a square on a piece of paper, from our perspective that square is flat. But in truth it was drawn onto a 3-dimensional piece of paper, and is itself three-dimensional, having length, width, and depth.
Now take a true 2D Square, only with width and length but no depth to speak of. Now stack another one on top of it, and then another, and then another, and do this infinitely. Is this 2D Square 3D yet? No, it still has no depth.
Even if this 2D Square has infinite width and length, it will still be smaller than a spec of dust in the 3rd dimension. Cause that spec of dust has depth, and that 2D Square even if stacked on top of itself infinitely, still does not have that extra measurement.
This can be repeated to the 3rd Dimension, no matter how infinite the 3rd Dimension is, it is unable to replicate an extra measurement of space.
Put simply, the infinity of a lower dimension is infinitesimal compared to the smallest possible size of a higher dimension's additional spatial coordinate.