The key is 'that obscure their true essence' - I wouldn't worry too much about what 'barnacles' (that is, "cultural barnacles") means
exactly here (that is, what its synonyms might be), just try to appreciate the image (i.e. the metaphor); that being said, 'encrustations' would make a good synonym if it weren't for the fact that there's already the verb 'encrusted'.

Hmm, how about 'useless and/or parasitic thingies'?
Actually, 'impediments' is kind of on the right track, I think

:
impediment
リnoun
1 the country's debt was a serious impediment to economic improvement
hindrance, obstruction, obstacle, barrier, bar, handicap, block, check, curb, brake, restraint, restriction, limitation, encumbrance, deterrent; drawback, setback, difficulty, snag, catch, hitch, stumbling block; informal fly in the ointment, hiccup, facer; Brit. informal spanner in the works; rare cumber.
-opposite(s): benefit.
(from the New Oxford Thesaurus of English)
