When we elect state judges, we increase one aspect of democracy and decrease another.
When most people think about democracy, they think about the aspect that political scientists refer to as “popular sovereignty.” That is, they think about the idea that the majority should rule. Electing state judges gives the majority more of an ability to rule. On the federal level, the majority gets to pick judges only in an indirect way because the president appoints judges. When the people get to elect judges directly, it gives them more control, more of an ability to rule. This is more democratic in that it increases the level of popular sovereignty in our system.
However, democracy is not only about majority rule. It is also about protecting the rights of individuals. For example, the United States was less democratic in the days when African Americans were denied civil rights even though that was what the majority of people wanted. When judges are elected, it makes them less able to protect the rights of unpopular people. Elected judges are more likely to go along with the majority if the majority wants to infringe upon the rights of some unpopular group.
Thus, electing state judges is both good and bad. It increases the level of popular sovereignty in the American system, but it reduces the judicial branch’s ability to protect individual rights.