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.
I don't think Binance is exempted from being "unhacked". They've got hacked years ago.
It's clear that no exchange is safe for us to store funds until now even if it's the best in the world. It's possible that Binance and Coinbase may get hacked again in the future, as these hackers are also improving their skills to create backdoors. Just saying.