The planet may indeed be a shout out.
You missed my point. Entirely.
The planet is one big city. Whether its a homage to Foundation or not, we can see clearly it's a big city.
We didn't need a character telling us as we are looking at the planet that it's one big city.
That would be like the Star Destroyer going to Hoth in Empire and and Ozzel saying to Vader. "Sir the entire planet is one big snowy planet."
They did get close. Han said that there wasn't enough life on this ice cube to fill a space cruiser. But by then, we'd already had our establishing shots of the planet, we got the idea already, and Han was speaking hyperbollically. The "It's one big city" was patronizing unnecessary exposition that takes away from the magic of Star Wars.
They never said Tatoooine is one big desert.
They never said that Endor is one big forest. They did say it was the forest moon of Endor, but that was used casually as a label.
Meh. Forest moon of Endor is close enough.
The crawl of TESB said "remote ice world of Hoth," so
we already know that by the time Ozzel is introduced.
You're right, though, I really don't see what you're complaining about.
Getting back to Coruscant, first of all, you're wrong that we can "clearly see" that it's one big city. We can see from space that the whole planet seems to be covered in structures, but—and here's the key—we don't know what they all are, as we obviously only see a tiny fraction of them up close. Without that line of dialog, there is no explicit allusion to
Foundation. Ergo, making the allusion was something that Lucas considered important enough to warrant a line of dialog to accomplish. Secondly, if you'd read
Foundation, you'd recognize the line for what it is, because that's pretty much exactly how Trantor is described in the book, page 12 (31st paperback printing by Avon Books): "All the land surface of Trantor, 75,000,000 square miles in extent, was a single city." Ric Olié's line, "Coruscant… the entire planet is one big city," apes it.