Some cats can thrive on plant based food. A bit like Huel it has some synthetic vitamins and minerals added. For example taurine, which in all commercial cooked cat food both vegan or meat based. Most taurine now is a vegan variant.
There are several plant based cat food manufacturers, food approved by vets. Bearing in mind that much commercial food is full of veg., grain, rice, charcoal and loads of other stuff.