Why not have all citizens vote for or against legislation? Online for instance?

Even if everyone had internet access or some other way to register their opinion, there are several problems with everyone voting on everything.

Most people do not have time or interest to properly deliberate about complex social issues.

Plebiscites, referenda and polls about complicated matters mostly reflect the opinions of the uninformed.

Demagogues can easily manipulate uninformed masses with emotional but untrue appeals.