Constituent powers can be separated into two broad categories: primary and secondary powers. Primary constituent powers are the ability to draw up a new constitution, while secondary constituent powers are those which allow for the amendment to an existing constitution.
Even when a constitution is unamendable, voters retain primary constituent powers. Incoming democratic governments can draw up a new constitution at the behest of the public. Just because they cannot amend an existing constitution does not mean democratic constitutional change cannot take place in any capacity. Therefore, unamendable constitutions are compatible with democracy.
Overcoming an unamendable constitution and necrocracy by drawing up an entirely new constitution is a waste of time and money and opens the door to democratic instability. If a government has to throw out all aspects of an existing constitution and start again from scratch to make a minor constitutional amendment, the process of updating a constitution would come with substantial risk. Institutions could be undermined, the public could lose faith in the democratic process, and fundamental human rights could be at stake. This leaves an unacceptable margin for abuse in the amendment process. By undermining human rights, democratic institutes and political stability, unamendable constitutions go against the core values of democracy.
[P1] Even under an unamendable constitution a government retains the ability to draw up a new constitution. [P2] This means the public can enforce constitutional change. [P3] Therefore, unamendable constitutions are compatible with democracy.
Rejecting the premises
[Rejecting P3] Drawing up a new constitutions increases instability and leaves a nation vulnerable to human rights erosions and abuse of powers. Democracy values political stability, human rights protections and democratic processes. Because unamendable constitutions threaten these values, they must be considered undemocratic.