If I'm going to do my take on a Traveller setting I think I ought to ponder the Fermi Paradox. This basically asks, "Where the hell are all the <censored> the aliens?" In an ancient and vast universe where is all the intelligent life?
Most answers to this problem involve most of the aliens blowing themselves up before colonizing the galaxy. That's kind of a pessimistic view. It means that all these aliens managed to destroy themselves without ever managing to create at least one offworld colony to survive their equivalent of World War Three. It also means that our intrepid explorers will encounter many radioactive cinders with little of interest besides tech a few centuries out of date.
Perhaps instead races usually develop interstellar travel after they already reached some new level of intelligence (or even a new kind of existence.) Humanity might be one of those very rare precocious races to find their way into FTL and discover a universe full off ancient brooding ruins and younger pre-starflight cultures. If the ancients are around obviously they aren't interested in talking to the likes of us or exploring anymore (they already know where everything is.) They'd probably view attempts by us to contact them as we would a caveman entering our home and playing with our pc.
So the rare starflight capable younger unevolved races would have centuries or millennia of empire building before they too achieved this ascension and left our universe or turned inward (leaving all kinds of goodies for pcs to find.) Races building interstellar empires like us would be fairly rare and hundreds or thousands of light years apart (considering we've had radio for over a hundred years the minimum average distance must be over 100 light years.) At the very least empires would be months or years of travel apart even at FTL speed and have many minor races within them.