I don't see why they would be bad.
They are used to remind humans about wildlife and exotic animals. Specially kids, who tend to be fascinated by animals since little, are taught to learn about them this way - and a zoo is simply amazing to their eyes. Personally, when I was little, I knew everything about animals - their names, their species, what they ate, their habitat... So I loved going to the zoo!
Of course, zoos are good when they meet the requirements - wild animals requires space, excellent maintenance (vaccins, food, etc), so it's basially a huge responsability + investment.
With the current world's situation, expansions of territories and whatnot, I guess animals are running out of places to live, which is sadly, unavoidable? Zoos keep us in contact with the amazing species on earth while safeguarding them, providing them their own spaces and making sure the offspring is healthy.