Well, there's always room for improvement. Personally I'm all for shifting more zoo focus to education, and entertainment value can still remain intact. Zoos are basically animal museums, and there are plenty of museums that work to be fun AND educational.
Though I think if we want zoos to be more educational, and do more conservation stuff, public image might have to be changed. In the mainstream, zoos are treated more as fun places to take kids and look at the pretty animals. Lots of people aren't going to zoos with intent to learn, and often mostly have interest in just seeing a few select animals. Maybe have advertisements and awareness campaigns to get people interested in the rarer, obscure species. There's no such thing as a boring animal.