It depends. Humans vary and, while you may thrive on a plant diet, you can't generalize your experience. There are people who have problems even supplementing B12. Others don't. You can't just tell those who have that they've been living a lie.
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"
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.