But the valuable use-cases could be solved using other methods efficiently.
If you mean more efficiently then that is likely a dimension of the solution where it may not fit for some use cases. For example blockchain transactions are known to be slow when compared to say a RDBMS transaction. If you are recording purchases in a web shopping cart its probably not a good solution. The trade-off here is that for some problem, maybe the speed of the transaction is not a concern.
Don't get me wrong, I'm not defending, nor supporting blockchain solutions. Just pointing out that the "we have ways to solve those problems already" isn't a very valid argument in software.