If human intelligence is so boring and non-special, how exactly did LLMs get this smart? Is it not from a) being developed by humans and b) being fed a very large portion of all human-generated text?

Without the human intellect to emulate, LLMs would be nothing.

LLMs learn from patterns in human-provided data (and soon each other and directly from nature). Humans learn(ed) from patterns in nature-provided data, and eventually each other (and, increasingly, LLMs).

There are many here who hate humans I think.

Prob because their life sucks.