I think this fear comes from a lack of understanding of "the system". In truth there is no central system. There is no server to hack.
I find it interesting (and you should too) that the computer scientists who know the most about "the system" of bitcoin are 1 - more likely to buy bitcoin and 2- less fearful of someone "hacking the system". It's just not possible.
It would be similar to saying you don't think email is a viable long term means of communication. YOU might get YOUR email hacked. Yahoo might get hacked and expose lots of people's email. But "email" itself is not going to crash or become unsustainable.
What about a mass EMP event?
The Bitcoin blockchain “system” cannot be hacked. Period. If you allow another person, company, organization to hold your “Keys”, or if you hold them on your own internet connected computer, That could be a real problem.