I don’t know that it is, though. Can you show me form of blockchain in the real world where this doesn’t apply? Saying large actors can’t affect a specific piece of internet technology, so far, is rather like teaching physics without friction. It’s nice and fun and easy to understand but completely ignores the reality of any implementation.

If login tokens are stored on a public ledger replay attacks write themselves. Public or private, keeping every login token ever is a horrible audit mechanism and doesn’t scale well. At scale, speed to generate becomes a concern. Not at scale, something lighter is faster.

A normal database scales better than a license blockchain and doesn’t require extra computation to write. Audit logs and hashes prevent extra edits. License files signed by a central authority don’t require a database and the central authority is functionally equivalent albeit less expensive than a blockchain.

I am still interested in a good use for the tech. I have yet to see one that is genuine.

As I understand, it's normally append-only. But, with some implementations, if a malicious entity controls most of the block production, they can undo recent transactions at will.

Go ahead and prove me wrong. Show me blockchain implementations that are immutable post append. On my end, we can talk about Bitcoin forks. We can also talk about the current state of consensus mechanisms, each of which has the explicit ability for large actors to rewrite history in their favor. Even Monero is susceptible because this is fundamental to the blockchain in any form. It’s been a huge reason why I make sure I get paid up front for any consulting I do in this space.