Greetings George,
The Ka’bah is not an object of worship of Islam, nor does it mediate through to God or anything like that. It is just a compass…like a focal point to get all Muslims on the same page, so they can pray together without facing in all which directions. Whether there’s a cube there, or a pole or a sign or whatever or even nothing to mark the spot…the purpose is unity action.
The Ka’bah itself is actually a house of worship, just like a mosque (albeit very small). It’s actually a small mosque inside a bigger one encircling it.
The difference between Muslim and Catholic worship is that when Muslims bow and prostrate on the ground, they do it wherever they’re praying, no matter what’s in front of them, a tree, a wall etc., because the humility the bowing and prostrations represent is for God alone, and God is everywhere.
On the other hand, Catholics and Orthodox will not bow or prostrate except before a statue or icon, which does become idolatrous because one is really physically humbling himself to a man-made work, like a stone sculpture or painting.
Now, before everyone seizes on me with outrage…I can appreciate that Catholics aren’t actually worshipping the statue when they do this, but still…one can acknowledge worshipping only a certain thing in theory, but by his actions suggest that he does something else than he says.