Blockchain technology is going to change everything: the shipping industry, the financial system, government … in fact, what won’t it change? But enthusiasm for it mainly stems from a lack of knowledge and understanding. The blockchain is a solution in search of a problem.
Yes, it doesn’t have any method for distributed global consensus. Instead, everyone gets to decide what they think the “tip” should be. Signed commits can give you insight into what others think it should be, though.
If I fork bitcoin and and replace proof-of-work with signed blocks, I would argue that its still a blockchain, just not decentralized. This would still be useful because others could see if I tried to re-write history.
I think of a blockchain, simply as a chain of blocks where each block contains a hash of its contents + the previous blocks hash. So, their primary feature is being an append-only tamper-evident database.