This is good advice but not really recommended because the safest thing you could do is save your cryptocurrencies in your personal wallet and no 3rd party exchanges are involved because they have their own owners and are prone to hackers and scammers. In order to protect your crypto especially when you have a huge amount of it, you need to acquire a hard wallet that has some good security and convenience to use because you gonna save your crypto there for a long time when you want to save and hold certain coins for long term.
What good does it make to use a hardware wallet when you'd need to eventually move your coins for trading? The security lies in the exchange itself. Not your wallet. Your best bet would be to only send the amount your willing to sell in a centralized exchange. For large amounts, decentralized exchanges (DEXs) would be the way to go.
People just need to follow proper security measures to avoid losing it all in an instant. It's just that the majority is not willing to put their time and effort to do this. Everybody wants "the easy route". Convenience goes on top of everything else, right? Hopefully, people will realize CEXs aren't as safe as they claim to be. As long as decentralization wins, nothing else matters.
