How does that matter? If they can get all the nutrients from plants why not give them food that is vegan? Their interest in taste is not a justification to violate another animal's right not to be enslaved.
The animals interest in taste certainly has to be taken into account for their well-being. And especially for cats, chewing on a tough meat-like substance is also necessary to maintain dental health.
But I don’t see how the pet benefits from the murder of another animal. There is no fundamental reason that prohibits a diet for pets that does not result in animal suffering. As long as nutritional components, taste, and texture fulfill the requirements, there is no reason to object to a vegan pet diet. But of course, not every vegan diet fulfills these conditions, and especially for cats, we are still learning how to best implement that kind of diet.
That is why I argue that getting a pet should be like adopting a child. You care for it because you love it. And no matter what, the pet or the adopted child has a right to not be used or be harmed. I think that getting a rescued dog and caring for it is a very noble thing to do. But breeders are hell holes. And while using a lead on a dog might remind one of slavery, remember that it is in the dogs greater interest to not run onto the street and other people have the right to be safe from your companion animal.