As far as I can tell, this is completely false. Vegan diets do a lot of things well: reduce salt, saturated fat, and cholesterol intake, for example. Vegetarian / vegan diets improve cholesterol, blood sugar levels, and other things.
Here's some citations of studies and papers that demonstrate vegan diets are better for you:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3662288/
Several more listed at https://www.healthline.com/nutrition/vegan-diet-studies#sect...
https://www.ncbi.nlm.nih.gov/pubmed/26508743 https://www.ncbi.nlm.nih.gov/pubmed/25684089 https://www.ncbi.nlm.nih.gov/pubmed/23695207 https://www.ncbi.nlm.nih.gov/pubmed/16164885
The consensus of scientific evidence seems pretty clearly in favor of plant-based diets. The evidence is as clear as the world being round or climate change being real.