How do we honestly justify keeping animals in zoos in this day and age?

From the most pragmatic standpoint animals are on display to get funding for conservation. Needed funding that would not be there without the zoo. To that effect there should be stipulations for zoos along with regular checks not unlike health inspections for restaurants. In the most ideal world we wouldn’t destroy habitats to begin with so conservation wouldn’t be necessary or at least we would properly fund conservation without zoos.