Suppose there's freedom of religion: everyone can choose what religion to practice. Is there some sense in which this is "undemocratic"? Would it be more "democratic" if the democratically-elected government declared a state religion, and everyone had to follow it?

You could, in theory, define "democratic" this way, so that the more areas of life are subjected to the control of a (democratically elected) government, the more democratic your society is. But in that case, the most democratic possible society is totalitarianism - a society where the government controls every facet of life, including what religion you practice, who you marry, and what job you work at. In this society there would be no room for human freedom.

https://astralcodexten.substack.com/p/bad-definitions-of-democracy-and