> One of the central points of a Constitution is to mark certain things off-limits to democracy.
This only applied to federal portion of "democracy" until the 14th amendment which added restricting the states re Bill of Rights. 14th wasn't adopted until 1868. I don't think it's that central.
> The Due Process Clause prohibits state and local governments from depriving persons of life, liberty, or property without a fair procedure. The Supreme Court has ruled this clause makes most of the Bill of Rights as applicable to the states as it is to the federal government, as well as to recognize substantive and procedural requirements that state laws must satisfy. -- https://en.wikipedia.org/wiki/Fourteenth_Amendment_to_the_Un...
The Constitution is primarily about limiting the powers of the Federal government vis a vis State government, and then both vs people. As outlined by the 10th amendment.
> The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
The government can't pass laws against "Turtles Suck!" because that power is not granted them. It is reserved to The People. This is why "people" like youtube and twitter and cancel culture are free to censor and ban.