There’s a good discussion of the lobster/human serotonin difference here. There are some valid semantic issues about how this discussion should be formulated, but once you delve in, that’s it. It certainly doesn’t undermine Peterson’s point that lobsters form hierarchies — in fact, without brains it just makes hierarchies seem more fundamental.
The big question the left can’t answer is, how we will decide what “better human decision making” to replace hierarchies is, is without imposing hierarchical power?
Look at the U.S. right now — the entire country agrees that half the country is insane, and we disagree about which half is insane.
In that sort of environment the only way “better human decision making” can replace hierarchy is by holding a gun to half the country’s head. Thus, of course, creating an immediate hierarchy based on who has the most physical force to impose.