I’m reiterating what my fellow Greeks are saying, but to be really really explicit:
- The metaphorical meaning of Philistine (Φιλισταίοι) to mean someone anti-intellectual is absent from Greek. The typical words would be άξεστος “uncouth”, χωριάτης “peasant”, (learnèd) άμουσος “un-Mused, alien to the muses”, (Turkish) χαϊβάνι “animal”.
- Λεξικό της κοινής νεοελληνικής says that άμουσος = “uncultivated” is old fashioned, and the current meaning is “unmusical, without a musical education”. Shows you what kind of Greek I’ve been reading…
- As Alexandros Gerofotis (Αλέξανδρος Γεροφώτης)’s answer points out, the metaphor that has persisted is λακωνικός “laconic”. People know the stereotype of the uncompromising Spartan,and people would get your meaning (especially if you prefixed it with σωστός “a proper”, which emphasises that it is metaphorical). But they would think “bellicose” or “patriotic” rather than “uncompromising” or “aesthetically bare”.
- For the latter (“spartan decor”), we use λιτός (as in litotes), the term the Spartans themselves would have used. For the former, αρβανίτης “Arvanite, ethnic Albanian” would be a more up-to-date allusion, but it is also more derogatory. The Venetian loanword ντούρος “upright, unbending” would also work.