Could you elaborate on the several reasons in your last sentence, possibly by pointing towards some sources?
In the Athenian democracy minorities were inter alia excluded from political decision making - one had to be a male member of the ethnic majority to participate, there was no mechanism for obtaining citizenship other than blood.
However - in comparison to how other Greek cities treated them, metics (resident aliens) in Athens enjoyed far greater security and had codified rights.
To me this latter point is decisive in showing that the horizon of direct democracy is always towards greater inclusiveness. But one has to make up one's own mind on these matters.
But back to the point i dont think you can compare business with societal structures. We are not doing democracy because its more efficient. Its extra effort we spend in hopes to achieve a better society. People have an entirely different stake in their job as in society. For your job the hassle is likely not worth the trade off (if there are any for an employee).
And back to OP
>A lot of people who advocate flat or structureless organizations actually have philosophical problems with even direct democracy for decision making.
I have to agree with the statement. The "real" democracy as a solution to the problem of organizations falls short. Crimethinc had an interesting article on the topic (which got turned into a book later) https://crimethinc.com/2016/04/29/feature-from-democracy-to-... . Its their usual over the top approach but an interesting line of thought.
Although, you lost me here
>Smaller objections to things like elected positions and parliamentary procedure, which are seen as too hierarchical.
I wouldnt say proponents of non hierarchical forms of organization have less of a problem with the representative approach.
One reason is that representation by definition focuses on people and trust in them (you are selecting "your man"), as opposed to issues. Some politicians try to incite inter-group hatred, because it is a strategy that pays off in this game. This brings out human ingroup/outgroup biases and that then causes issues for the minorities. (We have some evidence that people in Switzerland do not see "losing" in particular referendum as a big deal, they understand that the minority is adhoc.)
The other reason is that representatives are typically given authority over bunch of issues bundled together. So majority might vote in a representative because they agree with their economic policy, but they don't neccessarily agree with his, say, immigration policy. In fact, for less important issues, the elected representative can have completely minority opinions!
That means that unless the majority has horrible opinions (which it rarely has in actuality, and then it's questionable how any form of government arising from that culture could deal with this case anyway), there is always a risk of voting in a representative with a horrible opinion (and authority in that matter). While in direct voting, this issue would have to break the majority boundary, which it often never will. (Direct democracies are quite conservative in the real world.)
An example is Donald Trump's treatment of problem with ICE. Even if large majority of Americans disagree with how ICE treats immigrants, lot of people approved Trump (for other reasons), and he pushed (because what a person he is) for bad policies in that matter.
Furthermore, if you actually use utilitarian morality (which is disputable), and calculate the mean value of the bad policy effect on the minority over all possible distributions of minority and agreement with a horrible policy towards said minority, then you will even get the result that the representation is objectively worse (in the probabilistic sense) than direct vote on the policy. It is because "tyranny of the minority" (selecting a wrong person as a representative) is, it turns out, overall a bigger issue than "tyranny of the majority" (the former can work against both minority and majority, the latter only against a minority).
As I said, I can't give references, but the above would certainly be a worth pursuit. There are some people in direct democracies (Switzerland) studying it, but it is rather small number of people.