I agree. The whole point of a blockchain is to make it difficult to change a block after it's been inserted. This is normally done by making subsequent blocks

I agree. The whole point of a blockchain is to make it difficult to change a block after it's been inserted. This is normally done by making subsequent blocks dependent on the value of previous blocks in some way (e.g., hashing). That makes it hard to change an earlier block without also altering every subsequent block, which is a problem of an entirely different order of magnitude than just changing a single block (particularly if generating the hashes is computationally expensive). A normal linked list has no mechanism to avoid block substitutions. Entries have absolutely no dependence on the contents of previous entries, and can thus be swapped out at will.