It's not really clear to me what a true democracy means since it's unlikely that best leader/best lawgivers correspond to most likely to be elected. In a small community electability is somewhat of a proxy for skill in governance but that's not true as the size of the electorate scales and the skill that elections select for becomes more weighted to marketability and salesmanship. Those are important skills for leaders to have but they are probably not the most important.
Agreed. And it's interesting that (collectively) we like to believe it was.
> there have never been true democracies that scale up
I'd put modern Switzerland forward as an example of a democracy that has scaled, perhaps to the extent a fair democracy can be scaled. It's a country of 8.5 million people, speaking several languages, split into 26 cantons, and further into local municipalities. There's a tradition of defaulting to local rule. Cantons are the size of counties in the U.S. but are more powerful in some ways than U.S. states - they collect taxes, administer health care, etc. If you don't like something you can lobby the representatives of your canton personally. You may have even gone to school with the people serving there. And the people have the power, at every layer of government, to petition for a referendum to add or delete any law or amendment. The politicians respect that the people can veto them. [0]
Political scaling is an interesting topic. Leopold Khor wrote a book called "The Breakdown of Nations" which talks about how bad the scale of the modern nation-state is, the brainwashing required to sustain such an unnatural construct, the bullying that inevitably ensues given such a concentration of power, and, like you said, the loss of anything resembling a representative democracy, an inevitable slide towards authoritarianism. [1]
[0] https://wolf-linder.ch/wp-content/uploads/2010/11/Swiss-poli...