AFAIK this was a well-known problem for digital currencies. I think it was "eCash" that went the furthest ( https://en.wikipedia.org/wiki/Ecash ), with "blind signatures" to prevent transactions being linked to the same user, but couldn't solve the centralised trust problem.

BitCoin's "solution" is to share a ledger, pick the longest in case of forks, prevent spam using Hashcash and keep the hashcash barrier high by turning mining into a lottery.

This is a pretty cool hack, since it addresses not only technical security concerns, but also economic and social aspects. Yet I see it as a pathological, brute-force edge-case: technically a solution, but less "this problem is now solved" and more "ha, I hadn't thought of that; we'll need to specify the problem better".

I agree though that further discussion would be necessary to find that nail for blockchain, but the elephant in the room (Bitcoin) has people who are personally and financially invested, leading to incessant noise being constantly generated around anything related to blockchain.

100% agree. If you look at all of the current blockchain "use-cases" you will find that many of them (e.g. Ripple and Corda) are simply centralized/semi-centralized solutions that have been around for years (in the distributed-systems literature) masquerading a blockchain solutions.

In a sense the blockchain craze is good as it's getting institutions such as banks to modernize their systems and make it so that a regional bank doesn't need to wait 5-7 days to transfer money, but examples like this are few and far between and for the most part people are using the idea to drain money from undereducated/uncritical people.

The mentality that you need to have a problem to solve in order to justify your company has some real value to it. However, somehow this has expanded into the notion that every piece of tech that doesn't solve an explicit problem has no value. The existence of the gaming industry shows that this is not the case.