The only required supplement for vegans is B12, and that's not because of lack of meat. B12 is produced by bacteria and most of us live in sanitized environments, so there is no reliable sources of B12 any longer. It's possible that even the animals you eat are low in B12 due to cobalt deficiency in the soil[1], so I encourage you to check your levels and supplement if necessary.
Also, your argument is a classic example of an appeal to nature[2].
1: https://www.agric.wa.gov.au/livestock-biosecurity/cobalt-def...