I don't think it should be stated as universal. Some blockchains can have immutability as their absolute raison d'être, others may have it as an important goal,

I don't think it should be stated as universal. Some blockchains can have immutability as their absolute raison d'être, others may have it as an important goal, but may sacrifice a certain degree of immutability for other features. Whatever is going to happen, monoculture won't be the solution.