A purely peer-to-peer version of electronic cash would allow online
payments to be sent directly from one party to another without going through a
financial institution.
And which flaws are preventing it from achieving this stated goal?
Some of them:
* Payments cannot be reversed, even when coins are sent to addresses that non one has the key, or as a result of crime. That makes it unacceptable for most comercial and individual uses.
* Users are anonymous, which makes it much more attractive to criminals (much more so than cash, for obvious reasons).
* The fixed supply created the expectation of fabulous gains that turned it into a speculative pyramid schema
* That "ponzification" in turn resulted in extremely volatile price, that makes a bad currency.
* The block reward and the market price were too high, leading to a hypertrophied and unsustainable mining industry.
* For that reason, the cost per transaction is way too high.
* Mining got inevitably centralized (last time I checked, the top 5 Chinese miners had 60% of the hashpower).
* There is no mechanism to reward the relay nodes, which carry increasing load.
* Its design cannot support 1 billion users, maybe not even 10 million, even indirectly.
And a few more. Before you say it, yes, I know that many bitcoiners see those as advantages rather than flaws.