Earlier quoted context omitted.
OP's point is that you can write anything in the constitution - that it can never be changed, or whatever - but that's of no value whatsoever, if a large majority of people agree and decide that it's an invalid document.
That's a corner case, though. Anything is possible if you can get enough people to simultaneously adopt a new intersubjective[0] belief. In reality, changes in laws happen when a small group supports them and, small opposition notwithstanding, vast majority of people do not care . One of the easiest ways to make the majority care - and oppose you - is to push your changes in a way that violates existing legal framewo…
You cannot simply write down a law prohibiting becoming a dictatorship and then sit back thinking all will be fine, because then these groups will simply grow their power until they can ignore the bits of the law they don't like. And they don't need to change the law to gain power, they merely need acceptance of their telling of events.
On the other hand, without extensive support you cannot create a dictatorship because that word implies such extensive societal control that there simply must be extensive power behind it for it to function at all.