Drawing two crosses on a piece of paper every couple of years has really nothing to do with democracy. Democracy is when one can vote on all topics on any level (local village, town, district, county, state, ...) using the computer at home. This is possible to implement using the algorithms/data structures available today. We actually do basically everything online today - except voting.

For instance, such a system would be immune to corruption. That's one of the major reasons such a system will likely never appear.