Until there are actual serious studies with a large sample population from different parts of the world you can't be sure how many people will be affected and how. Also how healthily you eat is paramount. You can eat vegan trash too.
Btw, while I didn't say the line you're quoting about nutrients missing from plants, the article you're quoting is not very serious looking, with references that 404 and no way to find the actual data that I could find.
But it will be IMHO a miniscule percent/promile, not a majority.
> there are nutrients in meat that you don't ever get from plants
Plant-Based Diets Are Not Nutritionally Deficient https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3854817/
"More than a half-century of creative marketing by the meat, dairy, egg, and fish industries has produced fears surrounding nonexistent deficiencies, which in clinical practice need no patient monitoring by physicians and dietitians"