To write about oratory in ancient Rome was to write about politics. Since affairs were handled through speech, often public, the orator combined in his person the authority of the journalist, the essayist or public writer, the lawyer, and the statesman. It is worth remembering that this text was composed under a dictatorship (in the broad, not specifically Roman sense) which was then under one hundred years old.
An early speech, as a sort of misdirection, praises the style of the modern orators. They are more artful and engaging than the ancients. However, this is not a stable position. A man of great talent defends poetry on the grounds of its sublimity and because of the danger of oratory. Soon the causes of the decay of eloquence come under discussion.
There is a stereotyped criticism of education (Roman parents have slaves tutor their children, presumably teaching them slavish things). But this is soon followed by the politics. During the reigns of the first Caesars there was a reign of such moral decadence that the persuaders were replaced with flatterers. Once these habits of oratory are corrupted, we are told, they cannot easily be restored under the reign of a good and virtuous prince (which the present government obviously is. No question!).
The dialogue ends with an interesting speech to the effect that great oratory can only arise in a chaotic democracy. Under the government of a prince who wisely resolves all public questions, there is no place for the skillful combat of words. The interlocutors are told that they are blessed and fortunate to live in an age in which the art of great oratory is no longer needed.