Re: Merkle Tree
Short answer: It depends on the hash function.
Longer answer: In Bitcoin reversing a difficult hash is used as a form of proof-of-effort for distributing new coins. That's only one way to do it, although it's the easiest one to conceptualize because it involves real-world inputs with value (power and time.) If the goal is not to create digital items that are supposed to be a store of value, there doesn't necessarily have to be a high level of effort involved.
That said, yeah, a lot of stuff currently has "blockchain" tacked on it that either isn't using blockchain at all, or is using it as an inferior substitute for MySQL or MongoDB.