Cicero on the primary goal of oratory:
"As, therefore, the two principal qualities required in an Orator, are to be neat and clear in stating the nature of his subject, and warm and forcible in moving the passions; and as he who fires and inflames his audience, will always effect more than he who can barely inform and amuse them..."
Cicero describes the problem the OP reports:
"But let us return to Calvus whom we have just mentioned,—an Orator who had received more literary improvements than Curio, and had a more accurate and delicate manner of speaking, which he conducted with great taste and elegance; but, (by being too minute and nice a critic upon himself,) while he was labouring to correct and refine his language, he suffered all the force and spirit of it to evaporate. In short, it was so exquisitely polished, as to charm the eye of every skilful observer; but it was little noticed by the common people in a crowded Forum, which is the proper theatre of Eloquence."
Nuanced communication not working at scale, 2100 years ago.
[1] https://www.gutenberg.org/cache/epub/9776/pg9776-images.html
Nuance requires representing uncertainty and is higher complexity from accounting for multiple special cases. Placing more cognitive load and attentional demands on receiver.
Human communication is lossy and decoding can be non-trivial inference. Given that everyone comes with differing priors, the more finer grained and complex details are required in reconstructing message intent, the more likely it is to be misconstruected. Failing to attend to a single core detail can rend meaning.
At scale the chance for errors to propagate without correction increases.
Getting rid of fine grained details and communicating a lower entropy message inline with a crowd's biases also ensures it's more likely to survive in a form close to original intent. A good manipulative orator focuses less on truth or content and more on minimizing mismatch between receiver mental states and orator's directional preferences.
Actually it can be helped when everybody agrees that some information must be known by everybody. Communication campaigns, making it a subject in schools...
So the problem uses to be that there are opposing sides trying to beat each other. OK, that's obvious, isn't it? But come to think of it, is society so divided that most people's interests conflicts with somebody else's?
I understand that there are diverse interests dividing countries or continents, but often differences inside the same country seem to be artificially amplified and fuelled.
Both of those are basically so delayed and holey that you can forget using it for anything but the most basic points. Just look at how bad some people are at math and that's something both essential and taught extensively for basically the whole time one is in the education system.