nobody said not to use an exchange at all. but you definitely shouldn't be storing money there---using them as wallets---as many people do. the longer you hold your funds on an exchange, the more likely they are to be locked up or lost in one of these hacks.
just deposit coins-->trade-->immediately withdraw. that's the best you can do.
The issue here is that we can't do anything "immediately" as deposits and withdrawals on exchanges are not instant and then you need to trade them not at a dumping price as prices keep fluctuating. This atleast takes 2-3 days and sometimes a week in my case, I tried to withdraw my coins from exchanges and noticed they were charging half the coins as fee (which is not at all a feasible situation). We don't have many trusted exchanges and the ones that call themselves reputed are charging high fee which discourages the user from withdrawing their own coins.
Also, like Vishnu.Reang, I also have coins that have their own desktop and android wallets and when my online wallet got hacked, I stopped downloading wallets to store the coins and then exchanges became the only option.
Since now none of the exchanges are trusted, I have stopped accepting altcoins that come with their own wallet and asked the managers to hold them for me as I have no other option.
There is another solution(s), such as using DEX like Bisq or atomic swap, though not a lot of people prefer doing that way. You also miss important points from figment post that essentially said use exchange like an exchange, not a wallet.
So many people are storing their crypto in exchanges and never withdraw it due to various reasons, and that's why when the exchange got hacked they're rekt af. Sadly most of us learned the hard way, and that's why I believe case like Cryptopia or any other exchange won't stop unless customer also realizes their own responsibility.
Bisq and atomic swap require downloading a wallet which is not a solution. I agree that exchanges cannot be used as a wallet and I guess many don't even store their coins there but actively trade them. We can't blame them too as they keep depositing and withdrawing and such unseen hacks make them lose their money. Active traders are mostly at the losing end.