"They spoke the same language" ... not exactly, the Spartans spoke Doric, while the Athenians Attic. (Interestingly, there is a few Doric speakers left [0].) While those languages were related, their mutual intelligibility was limited. Instead of "Greek" as a single language, you need to treat it as a family of languages, like "Slavic".
"shared the same literature" ... famously, the Spartans weren't much into culture and art, and they left barely any written records of their own. Even the contemporaries commented on just how boring Sparta was in all regards.
If we delve deeper into ideas about how a good citizen looked like, or how law worked, the differences between Sparta and Athens are significant, if not outright massive.
While those two cities weren't entirely alien to each other, had some ties, same gods, and occassionally fought on the same side in a big war, there was indeed a huge political and cultural distance between them. I would compare it to Poland vs. Russia.
Not "entirely alien, had some ties" is not it. They were part of the same cultural cluster, participated in the same games, traveled to the same sanctuaries, had mutual proxenies. The very fact that we know the opinions of several Athenians about Spartans is telling. We don't know what they thought of inhabitants of Celtic population centers, or Assyrian cities, or Egyptian ones. But we know what they thought of individual Spartans that they mention by name, biographical detail and genealogy.
I stand by my comparison to the Slavic nations of today.
Yeah, we have a lot of opinions of one another, yes we understand basic vocabulary of our cousins, though details in fine speech are another matter, yes, we are technically Christian, but still the political and societal difference between, say, Czechs and Russians is quite big.
As was the difference between the Spartans and the Athenians. Constitutionally, the poleis were all over the map, from outright tyrannies, through oligarchies and theocracies, to somewhat democratic states.
So your argument is: Athens and Sparta had things in common but were different. Like Czechia and Russia. Czechia and Russia are quite different. So were Athens and Sparta?
"They spoke the same language" ... not exactly, the Spartans spoke Doric, while the Athenians Attic. (Interestingly, there is a few Doric speakers left [0].) While those languages were related, their mutual intelligibility was limited. Instead of "Greek" as a single language, you need to treat it as a family of languages, like "Slavic".
"shared the same literature" ... famously, the Spartans weren't much into culture and art, and they left barely any written records of their own. Even the contemporaries commented on just how boring Sparta was in all regards.
If we delve deeper into ideas about how a good citizen looked like, or how law worked, the differences between Sparta and Athens are significant, if not outright massive.
While those two cities weren't entirely alien to each other, had some ties, same gods, and occassionally fought on the same side in a big war, there was indeed a huge political and cultural distance between them. I would compare it to Poland vs. Russia.
[0] https://en.wikipedia.org/wiki/Tsakonian_language