I like you.

That depends on which humans and where. There are still plenty of tribes that live in areas where vegetation simply does not support their population. Luckily, humans evolved to be feed on more things than most things on the planet. We can eat plants, fungi, bugs, fish, etc.

So you’re right. Humans don’t need to kill animals. We can survive by killing just about any living thing on this planet. We can even eat things that would otherwise be super toxic to us by learning how to cook it, peel it, or skin it.

The bottom half is proof of why the top half was a bad idea.

Critical success and failure has never applied to skills. It was only ever in the rules for attack rolls and (in 5e) death saving throws. Critical success and failure in skill checks is probably an example of the Mandela Effect. Anyway, for the above reasons I don’t use them as such. However, on nat 20s I might provide a “path for success” where one may not otherwise have been possible. But it’s never a given. More of an opportunity for roleplay.