The original question was about a "meal that provides all the essential nutrients the average person needs to stay healthy over the long term"
The simplest, easiest, and the most correct answer is "just eat animals".
Of course, one can be "smart" about their diet, spend a lot of time on carefully balancing vegetables, fruit, grains and tofu, while also making sure to consume proper blend of vitamin and mineral pills and doing regular blood tests. BUT that's far from a "single meal", far from "easy" and "simple", and consumes a lot of time and mental capacity which many humans might not have a luxury to allocate in order to be fellows with farm animals, I think.
> The simplest, easiest, and the most correct answer is "just eat animals".
Stop right there. This is playing switcharoo.
You devised a hypothesis that elegantly goes like "healthiest simplest diet is what is closest to your own body". (And that you used as a justification to eat other animals)
But hey I guess the closest to your body is other humans. So seeing as you now backtrack and are not suggesting humans eat humans, thankfully you understand that the original question implies some norms about what is acceptable and what is unacceptable to eat even if it is contains all you need.
Now you just need to see why growing numbers of people think about eating not only fellow humans but fellow animals who are conscious, feel pain and suffer, especially the ones who grow up for consumption and suffer entire life tortured as unacceptable and you're all set.
In addition there is another "little problem" with your argument and that is that humans don't eat through by absorbing stuff like some sort of amoeba. It goes through complex digestive process that extracts some stuff from other stuff. And a bunch of stuff a human body can/should synthesize. Remember healthy eating is also NOT getting stuff you don't need and synthesize. And if you find the closest thing to what's in your body, that'll be a whole lotta stuff you do not need.
So no "just pick what's the same as your body" is not the most "simple healthy meal". On more than one level. It's just an excuse to justify a existing taste for meat.
As I understood your argument, you primarily don't like the idea of eating animals based on your beliefs, and you would oppose it even if animals were the healthiest food available ever. So I don't think we contradict each other here — I've heard you, and I understand your ethical position.
> And a bunch of stuff a human body can/should synthesize
You're 100% correct here, I am aware of that. For example, if you only eat meat, your body will synthesize glucose which it would be otherwise lacking (which technically means that meat does not contain the "optimal amount" of sugars).
> Remember healthy eating is also NOT getting stuff you don't need and synthesize
And also getting stuff that a body cannot synthesize enough. Like the notorious B vitamin pills that vegans pop like candy.
> It's just an excuse to justify a existing taste for meat
No excuse needed, god (or nature) made cows delicious — what do you think is the reason for that?
Okay, maybe a single food source won't give you all your nutrition.
Okay, maybe "just eat fatty meat" is insufficient.
Okay, maybe it's not just the food with the most similar composition that is best.
Average nutrition discourse on social media.
