This is like two old investors in buggy whips talking scaring people off of internal combustion engines. They have no idea what they're looking at but they'll make pronouncements anyway.

Bitcoin etc are currencies native to the network environment just as cash is native to the meatspace. Both have their advantages and shortcomings.

Wisdom is found in using things if they serve you and leaving them alone if they don't. Cash serves its purpose in the meatspace, cryptos serve their purpose on the network. Use them as they're useful.

I don't find it wise for anyone, Buffett or otherwise, to expound on things they don't know anything about. It's even less wise to take advice from those who speak from ignorance.