Your "soup" of STUFF, exactly.
But instead of thinking of the planet moving through the soup, instead think of the soup moving in all directions at once, but with variable flow rates in all directions at once .
all of that occuring in ever enlarging scale flows that leads to a general flow direction overall locally .
Then really FIX the planet, litterally not moving as such, and where all the flow patterns will give the illusion of movement of all other planets and moons, difficult indeed to do?
Then consider that We observe via the flows of this sea of soup stuff.
Thus any information recieved is been sent along the flow patterns within this sea.
Where ever the observer is sited , the signal pathways will re-inforce the illusion of movement.
I consider that Your soup is super dense, and that the information flows maintain a local series of fields about each fixed creation of mass.
That every finite point of that soup is and can be anything, space is where a reasonable flow exists near neutral alignments, a so called black hole been a perfectly arranged local geometric area that all of the soup desires to be so aligned as, and as such all signals are attracted and sent out again from that area.
Therefore nothing is moving as such, all is ONE, and any local field contained in that one is a constantly switching arrangement, not moving but switching, and it is the switching that appears as movement, and as each field will create its own resistance to any other field they will appear as seperate and independantly moving.