This is one view of things, and who is to say that that is the cosmos we live in. Do not take it to be definitely true, not without evidence.
An alternative view my spirit guide reminded me of is that the cosmos is always growing. Similar to how in information theory entropy is always increasing, one can say that perhaps matter and energy are always increasing as well. We know that both information and energy can not be destroyed only changed in form, but we can not definitively say that it can not be created.
For example, we know that in a vacuum it just so happens that random little particles tend to pop into existence, perhaps it is simply quantum non-locality, or some such, but it happens, so an absolute vacuum has not been achieved on earth, nor in the solar system. Indeed, even the Voyager spacecraft in interstellar space are still constantly bombarded with particles from the sun, the stars within our galaxy and those beyond.
So perhaps as time goes on, the galaxies will simply continue to grow. I don’t know what that would look like, but perhaps can explore such a cosmos vision in another story.