I'm not saying that with our vote we don't select our leaders - I'm saying that the reason why we have democracies isn't to ensure the selection of the best leaders (as the article was implying) but to freely express our self determination in legislative and governmental matters by way of choosing our leaders, using whatever criterium, reason, justification we please, just as we do with our personal matters.
That's fair enough but it doesn't render the whole issue void.
For example, a vast majority of the people might share the wish to select a leader best equipped to improve the countries economic prospects.
If that is what the overwhelming majority wants, but the system doesn't enable that outcome, then I think you can argue that self-determination hasn't been expressed.
If that was the case, would it mean that self-determination hasn't been expressed, or that its expression didn't reach the intended goal of those who expressed it?
I'd say that the article is criticizing the ability of democracy to deliver the latter, and that in a representative system the two can't be neatly separated.
If the system in aggregate produces candidates who can't execute what the people want, but yet each individual determines their own choice of vote amongst the poor choices, can this really be said to be self-determination?