I would not call it a failure as Bitcoin was never intended as a traditional currency. It was "created" as an electronic payment system based on cryptography and it has succeeded as a pseudonymous decentralized digital currency. And also it's just developing, it's just starting, sooner or later it will bloom and become a big time currency.
bitcoin is not yet capable in a system that adapts to fiat's financial system, there are many points that are not suitable, but bitcoin has its own business volume so it is not too obligatory to move to the existing financial system, bitcoin is still developing and has not reached the final limit, not worthy of valuation failed because there is still value for continuing development.