No it would not prevent the 2008 crash however if you had some money in a cryptocurrency you would be cushioned from some effects of the fallout. Not a replacement, just an addition. Having an alternative is the draw.
Blockchain scams are evidence of it's unreadiness and naivety.
Hard disagree, it's evidence of its effectiveness and maturity. No primitive financial system would be capable of being used for:
Pump and dumps, ponzi schemes, front running, market manipulation, rug pulls, and more
Financial systems are primarily tools for fraud and zero-sum transactions, there's a line there for what is and isn't legal which is decided by the government, but it's ultimately all just taking money from one place to another and someone loses.