Whatever works is my motto. For awhile I was eating virtually no meat, poultry or fish simply because I preferred fruit and vegetables. And I was conscious to combine veggies to create complete proteins. But my doctor said my blood work would be better if I would include some animal protein. So I still don't eat a lot of meat or poultry but I do eat some fish and I did become healthier.
Also all studies conducted report that people undergoing cancer treatment generally tolerate it better and stay healthier if they do consume substantial amounts of animal protein. Why? Dunno. But that's the results of several studies on the subject.
Certainly those who avoid a lot of processed foods, salt laden, bad fat, etc. are going to be healthier than those who don't avoid that stuff.
The Japanese people as a demographic are the healthiest, longest lived people on Earth despite a high salt diet. They have few issues of cholesterol and high blood pressure and their diet consists of natural vegetables and lots of fish and seafood. They do not consume much refined sugar if any.
Humankind has been carnivorous or omnivorous, rarely ever herbivorous, according to most paleontological scientist dating back at least to the Pleistocene epoch more than two million years ago.
Those early hunters probably didn't give a moment's thought to the discomfort of the animals they killed for food.
That humankind has now evolved to care about other creatures on Earth does not of necessity require them to be vegan or vegetarian. One can be carnivorous and still demand ethical treatment of animals. And in my opinion it is cognitive dissonance to care about ethical treatment of all animals but not ethical treatment of all one's fellow human beings.