Yes. I agree with all of this. There are assumptions. Coming from the "We see a goblin and don't even bother to give it a second look" or the "I'm used to walking into the blacksmith's and waiting in line with a dragonborn and tiefling," was the default for the original quote. Because the original quote discusses the Cantina, and none of them were staring at one another (except for Luke of course

).
And I do not think cultures erase - they assimilate. They grow together. They are added to. They expand. Not erase.
Having lived in Chicago, spend some time in Viet town or Greek town. They are, for the most part, like most of the other parts of town. A few more Greek restaurants, a few symbols engraved into the sidewalk, the smell of lamb, and an historic house or two.
Maybe going back in history we would see it more segregated. But once we get into the "hundreds of years" status, the culture has grown. America's most famous example is probably China Town in San Fran. Half of the reason it still exists is because of tourism. If it weren't for that, it would have probably become like any other part of San Fran.
As DM, we could have the races all segregated, and one part of goblin town pandering to wealthy merchants that like to go in and watch goblins climb greased poles and try the spit-beer?
I don't know the answer. I am just throwing it out there, that if all the D&D races live together and are on equal footing for resources, then the descriptions shouldn't be about races, but rather places.