Ambiguity leads to different interpretations in literature. Her in this poen I believe you are reffering to the terms like "something" which is reiterated.
Something there is that doesn't love a wall,
So the readers are allowed to guess and interprete what this something is. It may be modernism which is against of useless traditions, it may be nature (since Frost is a romantic poet) or it may be poet's mind itself doesn't like the wall to be mended. (since he is insisting in his neighbour of the uselessness of performing such an act)
A good range interpretations can make successul poetry so has this poem. But sometimes ambiguities can perplex the reader yet I believe ambiguity is a feature of success in any piece of literary work.