I don't think the author is gatekeeping here. The way I read your comment, you seem to be gatekeeping what is complicated enough

'Tis not a contest. Curiosity is its own reward.

The existence of more complicated things does not mean that other things are not also complicated.

Financial markets that are open to the participation of billions of people, amalgamating all the behavior of all those participants, are complicated. Perhaps not nearly as complicated as quantum chromodynamics, I dunno, but complicated nonetheless.

Flash cards are not understanding, and it doesn't help that few if anyone explains finance without a lot of handwaving and magical thinking.