I'd say the exchanges that currently remained to be unhacked are pretty "safe"; probably Binance and Coinbase. But that doesn't mean I'll recommend leaving funds on these platforms. The developers can make the platform as secure as possible, but never secure enough to the point that it's impossible to hack. Exploits will always be a risk. Not because these "unhacked" exchanges remained unhacked for years doesn't automatically mean it'll stay the same forever.
https://NotYourKeys.org How do you explain these things to the people whom have entrusted their funds and assets to you for safe keeping hoping that what they gave to you is under safe care only to wake up to a sad news of their assets being stolen by hackers. How do you explain all these.
That's why you don't let other people entrust their funds to you. You have not much to gain but everything to lose.
There is no way centralized exchanges can be safe. Although some reputable ones are safer than we think, but we dont know how the future holds for them. The reason why people should never entrust their coins in centralized exchanges in the first place, but it should be decentralized ones. But its always certain, the only way people will learn is to experience first the mistakes and losses before they start to realize that its not always safe having centralized exchanges around.
It would be never be safe, once you do deposit your funds into any centralized platform or simply you dont possess the wallet keys then make yourself that prepared and convinced that its not your money anymore.
Its one of the common or known risk that chances of hack and running away funds is mostly could happen even though not that rampant but dont make yourself that get confident on this situation.
This is why on the time that you had make use of these exchanges or simply had done trading then it would be always recommendable on pulling out your funds and
transfer them into those non-custodial wallets for much safer storage of your coins or assets.