Yes. The "Battle-of-Thermopylae-era Sparta" of which you might be thinking existed over 300 years before the Romans conquered the Greek states, including Sparta. A lot can happen to a city-state in 300 years. The Spartans during the Roman conquest would have regarded their glory days of Leonidas with the same separation that we in the 21st Century might think of Oliver Cromwell and the English Civil. The biggest Hellenistic contender against Rome by the 2nd Century BC were the Macedonians.