Currently looking into the following:
getEntityNamespaceLookup
getFullEntitySerializer
getCompactEntitySerializer
getBaseDataModelSerializerFactory
getCompactBaseDataModelSerializerFactory
getStorageEntitySerializer
getLanguageFallbackChainFactory
getStringNormalizer

Investigation Summary

While it is clearly apparent that services such as EntityNamespaceLookup and LanguageFallbackChainFactory are dependent on wiki settings and thus are non generic, it is not entirely clear whether the serializer methods should be considered generic or not, as they do depend on entity type definitions, which are registered by extensions. However, these type definitions can gracefully degrade to default wikibase repo settings. Therefore, a decision needs to be made as to whether services that are affected by extensions should be considered generic or not.