Zootopia is a bad allegory for racism because racism in real life is usually based on superficial distinctions like skin color. But in a world of talking animals, the physical differences between different animal people are so extreme that equality is fundamentally impossible.

A job suited to an elephant couldn't be performed by a rat, and different facilities would be needed for the different species. This is a world in which everyone would actually need their own water fountain, so there's no way the animals could ignore each other's differences.

In real life, there's no physical barrier to a black person and a white person sharing the same public restroom. But in Zootopia, a world of animals, a mouse obviously couldn't use the same restroom as a horse, so one of them will always have to walk further to find a toilet.