I think your reasoning is somewhat an artifact of bias in science fiction in the first place. You see presumption of FTL all over the place, and so it's depress

I think your reasoning is somewhat an artifact of bias in science fiction in the first place. You see presumption of FTL all over the place, and so it's depressing to consider that it is very likely a hard impossibility, because it rules out a lot of those stories. But, there isn't a lot of science fiction which explores the consequences of eliminating biological aging, or anything else which might make 1500 years actually a rather short span of time for intelligent life. Maybe the galaxy is full of life which thinks nothing of going on a journey that would take thousands of our years, or longer.