I don't know, maybe one day they will invent something whcih will make impossible to hack an exchange, but for now you are absolutely right. Btw IMO even if such a thing will be invented they still can be hacked from the inside so, yeah, it's better to not keep much coins on an exchange, ever.
TL;DR: Nothing is unhackable.
What country do you live in my friend ? I hope you are not living in a very poor country but still even there anyone can buy a PC with old parameters now like a Core2duo with 2 to 4 GB of ram. Even if you have a shared PC with other people you can create a user for yourself and set up your own desktop wallet there. Just make sure to install Mulitbit HD or Electrum and keep the seed safe and you should have no problems. Leaving the coins on the exchange is a very bad idea after so many "hacks" happening lately.
Well, it's never safe to store your coins in an exchanging site. After all, the people are all anonymous and they could use the "hack" card to just run away together with people's fortune. But tbh, one shouldn't store his coins in a single 'basket'. Some people that I talked with suggests that I store 1/3 of my coins in exchanging site, 1/3 in a gambling site, and then 1/3 in my wallet. The reason they suggest that is so that even if any of those 3 gets hacked, only 1/3 of your coins will be gone and not all of them at once.