We may conclude from the preceding discussion that the cases ought to be assigned a considerably less essential function than is sometimes suggested in scholarly grammars and often in didactic grammars. The meanings of the verb and nouns involved play a much more important role in the sentence. This relative lack of importance explains in part why the structures of the Romance languages could develop (practically) without cases, without communication problems of any magnitude arising. What changed was the system of formal marking of the semantic structure, which itself was largely based on the meanings of predicates and noun phrases. The case system has given way to another system of marking the syntactic and semantic relations, a system in which particularly word order and prepositions play an important role.
Pinkster, Harm (1942-) , Latin Syntax and Semantics [info], xii, 320 p.: ill.; 24 cm. [word count] [Pinkster].