Carnivores like cats can't survive on plants alone. There are sad stories of folks who thought they could feed their cat a vegan/vegetarian diet and ran into significant, debilitating issues with lack of taurine. I'm not saying it's impossible to feed pets a solely plant-based diet, but you need to do a lot of research to make sure their nutrient requirements are being met. I would definitely do this under the guidance and consultation of your vet. See: https://www.aspca.org/news/why-cant-my-cat-be-vegan
Yeah, seems like a bad idea without significant R&D into formulating a plant-based meat substitute suitable for a particular animal's diet.
What I'm potentially more interested in is whether cultured meat will be appropriate to feed to pets, which it intuitively should be if the tech lives up to its promises.
Isn't taurine artificially added to all kinds of human consumption products? I wonder if it would be good enough to create a meat substitute that contains everything cats need.