Maybe you didn’t see my link where loma linda California, mostly vegetarian seventh day Adventists live longer healthier lives than the general population....
And it can all be 5 to diet alone with no other confounding factors?
That’s not convincing.
At the very least, a vegetarians/vegan diet is B12 deficient, which is an important vitamin. And sure, these days we can take supplements, but if you are on a diet that requires supplements to round it out, that is proof that the diet is NOT adequate.
Eat vegan if you want but it’s not adequate nutrition for humans.