As usual, you are spot on. However, an exception should be made for initiatives that restrain obvious political overreach.
Constitutions should:
1. structurally define the legislative, executive and judicial branches, and
2. place limits on their powers.
If you’re a strict Constitutional constructionist, all initiatives, referendums, and other direct democracy applications are unconstitutional, since the Constitution guarantees each state a “republican form of government” in Article IV; Section 4.
“The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.”