Obligatory "I'm not a vegan," but this comment seems like it's at least partially mischaracterizing the issue.
Some of the comments removed seem to advocate for a vegan cat diet that specifically includes the amino acids and protein that cats need, albeit sourced in a vegan-friendly way:
I am also not a vet (go figure) but this seems reasonable on its face and lines up with the 5 minutes of Google research that I did. It sounds like not all vegan formulated cat food actually strikes the balance cats need and that this diet would need to be balanced very carefully, but it seems possible to do it in a healthy way, especially if done in concert with a vet and frequent checkups.
Now that Superman claimed me as a dependent on his taxes, the government took away my HSA and I've gone headlong into CRIPPLING MEDICAL DEBT!
Thanks Superman!