Failure or success will depend on individual thought process, I agree. Again I feel what Satoshi has developed is still being worked on and developed further - this shows that he has been successful in my opinion.
There will always be naysayers but looking at the big picture, I feel we have been pretty successful.
Government and their approach to bitcoin might be different but the point is that the use of Bitcoin has increased gradually aside from the trading of Bitcoin.
I agree with you, there is no right or wrong answer, it's up to what each individual thinks. Many argue that it has failed because it cannot become a currency or is not peer-to-peer but is becoming more centralized on centralized exchanges. But to me, bitcoin has succeeded, Satoshi was right when he created bitcoin, bitcoin is opening up many opportunities for us to help many people become financially free, and own their assets without any 3rd party. Bitcoin is not perfect, but it succeeds because it has helped so many people change their lives.
I am not entirely sure, I mean there is definitely a right or wrong in this case, we just don't know which one is which, because we can't get an answer and that is why it looks like there is no right or wrong. Since we can't ask Satoshi if he thinks it is failed or it has not failed so far, then we do not know the real answer, when you do not have that real answer the only thing left is to speculate.
That is why it is clear that we should not be working towards making assumptions neither, but if we ever do then there is nobody that could say we are wrong and back it up with facts, unless Satoshi comes out of the woods and explain anything, which we all know won't happen. The truth is "there", we just can't get it.
