One point, we already make the decision for our pets diet. You are already supposed to consult a vet or nutritionist if you care about ensuring the animal is healthy, vegan food or not.

Its not a moral decision for the cat in this case anyways, its in service of their health first and foremost. If the cat can't be healthy on a vegan diet, or just simply doesn't like it, then a vegan will look for the next best thing that could be the healthiest fit for their pet, and see how it goes.

Conversely, plenty of non vegan owners will buy whatever random food is sold in their box store, do zero research past a facebook/reddit corporate circle jerk, and then pat themselves on the back for being such great owners.

The simple fact that vegans are involving pet nutritionists should be a clue as to their priorities. You could also simply ask your vet about it, just like I did, and find out that they won't accuse you of animal abuse.

So it’s immoral to force your will on a cat regarding their diet when they themselves would choose different is immoral but forcing your will on cows/pigs by killing them even though they would choose to live is not?

Cats, like humans, need certain nutrients (macro and micro), they don’t need that nutrients from a specific source. Of course a healthy vegan diet needs effort and monitoring to ensure sufficient intake of these nutrients, but it’s certainly possible, both for humans and cats.