Two facts to hold simultaneously
The first fact is that Sparta produced the citizens the Greek world acknowledged as the most disciplined and the most reliable in battle for several centuries. The second fact is that almost no Greek state tried to imitate Sparta. Both facts are evidence the classical tradition is read against.
The Greek philosophical and historical literature on Sparta is large. Plato dedicates parts of the Republic, the Laws and the Statesman to thinking through it. Aristotle's Politics gives the Lacedaemonian constitution serious analytical attention. Xenophon — who knew Sparta directly, fought alongside it, and admired it — wrote the longest extant defence, the Lacedaemonian Constitution. Plutarch's Life of Lycurgus is the form in which early-modern Europe received the material. The amount of writing on a system nobody copied is itself significant.
The system
The institutions attributed to Lycurgus formed a system, not a list.
The land was redistributed equally among the Spartan citizens (homoioi, "the equals") with a serf population (the helots) attached to it; the citizen body was thereby freed from agricultural labour. The Spartan boy was taken from his household at seven into the public agōgē — a long sequence of training in arms, endurance and obedience that produced the soldier-citizen. The syssitia — the public messes — fed adult men in common, so that even at meals the household was not private but civic. Conspicuous wealth was prohibited; iron currency, deliberately heavy and useless abroad, made trade and accumulation difficult. The dual kingship and the council of elders sat above the citizen assembly with the five annual ephors as a check on both.
The arrangement worked. Sparta produced consistent victories in hoplite warfare for centuries. It was the polity at the centre of the coalition that defeated Persia at Plataea. It was the polity that defeated Athens in the Peloponnesian War. The institutional results are evidence that the system did, in fact, do the work it was designed to do.
What it cost
The cost was also evidence. Sparta produced few philosophers, almost no poets after the early period, and little extant literature of its own. The Spartan economy was sustained by the labour of an oppressed helot population whose periodic revolts were the structural fact the Spartan state spent considerable energy managing. The Spartan education for women — by Greek standards remarkable for its physical training and relative freedom — was paired with strict marital and reproductive expectations subordinated to the state's military needs. Aristotle's Politics records the long-term demographic decline: the citizen body shrank steadily over the classical period because the property-and-equal-lot system did not accommodate inheritance well, and Sparta could not, in the end, find enough Spartans.
The classical tradition saw all of this. The reason almost no Greek state imitated Sparta was not ignorance — Xenophon's defence existed, Plato's careful engagement existed — but a considered judgement that the trade was not one most polities could or should make.
What the tradition kept
What the long tradition kept from Sparta was not the institutional system but the demonstration. The demonstration was that a polity can, if it deliberately structures itself for the purpose, produce citizens of a discipline and martial virtue ordinarily found only in exceptional individuals. The Stoic moral tradition kept some of this under the name of askēsis. The Roman military culture kept some of it. The early-modern republican tradition kept the idea of civic education through Plutarch even where it kept none of the substance.
What modern readers should keep — and what the platform reads Lycurgus for — is the harder question. What is the discipline worth, and what is it bought at? The Spartan answer is one extreme of the classical inquiry into civic virtue. It is not the only answer; it is not the platform's answer; it is the reference point that helps every other answer become clear about what it is committing to.