Many open-source or commercial databases can be used in a distributed fashion (either as homogenous or heterogenous) to create a distributed “ledger.” Most cryptography (open source or commercial) is industrial strength, and timestamping isn’t a new idea. Those three combined — in software — can easily duplicate all of the “features” of a blockchain — except one.
What they can’t do (in simple combination) is solve for “double spending.” So where does the problem of double-spending occur? Cryptocurrencies (like Bitcoin). This is also why the first success of a blockchain was a cryptocurrency. It was also a compelling business solution for people who want/need anonymity (for a host of reasons — including illegal activity including laundering and tax avoidance).
That’s just the technology. The business challenge is even harder because in order for any “blockchain” to be successful — it requires voluntary agreement on the part of competing commercial interests that will increase their legal liability and decrease their revenue. Does that sound remotely like something healthcare will embrace?