If c is the issue, then some civilization will use solar systems as space ships. They'll figure out a way to move a star along a chosen path and keep the planets in orbit. The travelers would have all the comforts of home while wandering the galaxies.
In fact, I wonder if anyone has done that already. It seems like we'd be able to see their stars dancing about.
Yes it's a huge leap, but the leap might not be as big as it seems: if we can figure out artificial gravity, then maybe we can scale up the technology and move stars, leading to more fruitful space travel than metal ships alone can achieve.
OTOH, that method of travel would still be rather slow and aliens might have abandoned the idea because it's too boring.
In fact, I wonder if anyone has done that already. It seems like we'd be able to see their stars dancing about.