There is no doctrine to be found anywhere in the Dialogues. This means the Republic is little more than a commercial for philosophy.
The arguments are intended to be fallacious in the Republic, because this Dialogue was written in order to demonstrate the problems of a fanatical pursuit of justice. It admits philosophical Eros is unattainable, given the dilemma of the philosopher who is torn between the desire to rule and the declination to rule.
One of the forbidden fruits of philosophy is the Siren call of politics, where the foundations of the perfect city beckons. This exotic fantasy offers relief from our profound boredom with the banality of life.
I disagree with the traditional reading, for Plato’s adoption of the dialogue form should indicate his intentions, how he is to be read: non-dogmatically. The literary features of the dialogue are crucial for a robust exegesis.
Contra the traditional reading, I don’t think it is legitimate to presume that Socrates (or Timaeus, the Eleatic Stranger, or whosoever leads the discussion) was the mouthpiece or the spokesman of Plato. Rather than singling out a character in order to locate Plato, it is the entire dialogue who speaks for Plato.
The traditionalist may object and insist that there are recurring patterns across the Dialogues, but these patterns, the so-called theory of Forms or the force of Eros, are far too general to constitute a doctrine. At best, they are thought experiments.
It matters not that the Dialogues had philosophical content, or whether Plato himself held doctrines, but that they established the art of debate by offering up positions for critique. The reader is shown how philosophy is done, how to think and speak, and that he has an open invitation to the game of philosophy.
For example, in the 1st book of the Republic, Plato shows us how the question is always more important than the answer. That is the minimal doctrine, if one must be found. Another example is Diotima, whose presentation of the Forms is actually in doctrinaire form, rather than aporetic. Yet her vision lies beyond the limits of knowledge much like an oasis in the desert.
Therefore, the Dialogues are non-dogmatic because they are experiments in philosophy. Instead of dictating what is the case, or what Plato believed, these Dialogues actually show us how to think for ourselves.