Matter has a great deal of complexity. The construction of anything complex requires tasks in parallel and in series. It takes time. Therefore it must be ongoing. Old matter must assist in the construction of new matter or else new matter creation would be a separate miracle every moment. New matter creation therefore takes place inside of large objects. Therefore we see why the orbits of two large bodies must always grow larger and accelerate. Or matter would amalgamate, rather than orbit, meaning that no serious reality could ever have gotten started.
So yes galaxies grow larger. But if this process continued forever the universe would be crowded with mass. There is periodic culling. Every so often we expect Sagittarius A* to send out a shockwave culling moons, planets and stars.
Moons grow to planets grow to gas giants grow to stars and on to larger stars. But at any stage a shockwave from the centre can cause any of these to explode.