From the research I've done, I think the most responsible diet would be a mostly plant-based one, but with the addition of chicken eggs from a responsible source, along with a basic mineral supplement for calcium/iron
That being said, a lot of people (myself included) eat far more animal products, particularly meat, than needed
There are a number of factors at play there, including government subsidies for feed crops and meat production artificially driving up its availability
Humans are omnivores, and have been for the lifespan of our species
There are a number of important nutrients that humans get from animal products that are difficult to get from plant-based sources, including vitamin B12, which is not present in land-based plant species (I'm not sure whether red algae counts as a plant, so I'm playing it safe with land-based)
Funny enough, this painting was displayed in his house, and not shown to the public until after his death, so it was made for his own self, not the approval of others XD
From the research I've done, I think the most responsible diet would be a mostly plant-based one, but with the addition of chicken eggs from a responsible source, along with a basic mineral supplement for calcium/iron