Slaughtering animals for food is indeed a much bigger problem and probably one of largest issues we currently have - ranging over ethical issues, environmental issues, health issues and socioeconomic issues.
However, this does not mean that "smaller" problems are somehow not worth mentioning/tackling. IMO zoos, just like TV shows for children in which cartoon animals are portrayed to live happy lives on farms, happy cows on products, etc. are all tiny little but VERY effective weapons for the industry to manipulate people into thinking that using animals for profit is actually good, because the animals are said to be so happy. The opposite is true.
However, this does not mean that "smaller" problems are somehow not worth mentioning/tackling. IMO zoos, just like TV shows for children in which cartoon animals are portrayed to live happy lives on farms, happy cows on products, etc. are all tiny little but VERY effective weapons for the industry to manipulate people into thinking that using animals for profit is actually good, because the animals are said to be so happy. The opposite is true.