Veganism is...interesting.
The moral reasons for veganism are arbitrary and self-defeating. If you think it's always wrong to kill any animal life of species other than your own, and thus wrong to kill such life for food, your morality is absurd. Humans have been doing that for thousands of years. There are animal species that do nothing but eat other animals. Are they all evil? Are you petitioning to ban the use of cars so no one runs over squirrels? To ban windmill power generation so no birds get whacked? The real reason behind this isn't that they care about animals, it's that they hate humanity and don't think we deserve to exist in the first place.
Now, you can think killing animals for food is ok per se, but be critical of the modern livestock industry for how it treats animals before slaughtering them. On this vegans have more of a point. I can agree that we should do our best to treat animals humanely, that we have a moral duty not to cause them unnecessary suffering. That's fine. That doesn't require abandoning animal products entirely, though. Just choose brands you know treat animals more to your standard of humanity.
However - there are a lot of people in the world. A lot of mouths to feed. A lot of people with not a lot of money. And no, you can't just feed people with plant products (more on that in a bit). It's a good thing that we've gotten so good at raising animals to make animal products regularly affordable and available. If you can afford more ethically raised animal products, you're probably upper and middle class, living in a rich country that subsidizes that kind of thing. Judging lower class people, and people of other countries, for buying animal products that aren't up to your standards is rich upper class elitism, plain and simple.
Now what about the health reasons for going vegan? It's true that a person who switches to vegan will see health improvements - if they're switching from the typical "American" diet. The typical diet nowadays, sadly, consists of a lot of ultra processed high calorie, highly palatable food. There's not enough fruits and vegetables in that diet to begin with. Switching to vegan from that will probably cut down on ultra processed food, leading to less overeating and a lower calorie intake. You'll get more fiber, more micronutrients.
However, you can get all those benefits without going vegan, and going vegan has its own downsides. If you consciously add more fruits and vegetables to your diet, avoid ultra processed food and stick to lean meats, you're already on a pretty good track. On the other hand, going vegan leads to a deficiency in protein, and B vitamins. To be healthy as a vegan, you have to supplement. If supplementing a diet is required to be healthy, can the diet itself really be said to be healthy? There's also the matter that plant -based meat substitutes are ultra processed by nature, and negate that benefit if you can't go without eating something like meat.
Overall, the moral reasons to go vegan are kind of elitist at best and absurd at worst. And the health reasons are pretty much bunk.