So? Below average IQ doesn't mean that your opinions are valueless and shouldn't be taken into account.

We all have to live with one another, and to make a system of government work with peaceful transitions of power, everyone must feel as if they have a voice.

High IQ, high education, high wealth, and other social advantages can be leveraged into making side-channels in the political system (e.g. lobbying), or by shaping the discussion the general electorate sees (e.g. overton window) in order to direct it towards ones goals.

Democracies have all been implemented with specific factors to make them viable in today's society, not some idealised society.