I'd think about it this way - with LLMs I'm still a human with one brain, one set of hands, one keyboard, one screen.

I can delegate more quickly, but still I'm constrained to what I can respond to because I can focus on limited amount of thing at a time. It's like I was given multiple sets of hands (so your centaur parable stands), but that doesn't make me faster if I need to do multiple things at the same time - have you tried juggling, chewing gum and skipping at the same time?