It is true that exchanges you mentioned in your posts have maintained the trust of their account holders since their establishment, by successfully maintaining security of funds and mitigating hacking issues. We also need to acknowledge that exchanges play vital role for development and growth of crypto industry, and in providing liquidity for executing our trades. Despite all these advantages, it is in our best interest to maintain funds in our own wallets because past performance doesn't guarantee future results.
Even after these facts, we should still know and stick with the reality that it is still risky to hold a large sum of funds inside any centralized exchange because as long as we don't have the full power on our own coins, it's safe to say that it's not safe and we do not have 100% control of it. Even if it's the most successful and most trusted CEX in the planet, there are still no guarantees that it will be safe to store it.