I'd actually argue that crypto/bitcoin is actually quite safe for the long run.

Given the tokenomics of bitcoin, it is disinflationary and have a capped supply. So long as there is no massive failure to the network it's hard to see how its value will underperform fiat over the long run.

But diversification is certainly key especially if you are looking at risky assets like crypto. Diversify both within asset classes and across asset classes. Even if you are the most ardent crypto holder, you should diversify in fiat assets like stocks to cover your back.