The value of bitcoin lies in its immutability. That's the only thing it really has left going for it.
Bitcoin is not immutable. The current chain would make absolutely no sense to a (full-validating) client from 2011 due to various additions and protocol changes.
What it is, as a project, is being extremely conservative, but that's a human political value, not a property of a technical system.
I'm referring to the immutability of issuance and balances. That's the type of immutability that matters.