It's true that there is the assumption that technology and innovation will reduce interstellar travel times drastically, the way they have reduce travel across an ocean from many weeks to a few hours.
I do agree that most people probably are off by at least two orders of magnitude in estimating realistic interstellar travel times. With technology we can predict as probably going to happen, we're still on the order of hundreds of years to even nearby star systems.
Unless some magical technology breaks the light-speed barrier, space will not be "another ocean".
However, star-faring civilisations are still possible. They wouldn't be any kind of space kingdom, but independent star systems that just happen to have a common ancestry. They would certainly communicate, and the technology for that basically exists already, at least in the nearby area ( And if we can only travel to a few of the nearest stars, would we want to? Is there anything there we want?
Humans do a lot of things simply because we can. And what is vast resources today isn't so much tomorrow. Just 200 years ago, all the gold in the world wouldn't have enabled you to fly to another country for a quick visit to relatives. King, pope, peasant, no difference, simply wasn't possible. Today, anyone with an average income can do it.
So in another 200 years, who's to say that a space ship to a nearby solar system is not well within the budget of a wealthy nation?