I agree some things I wouldn't do. Any parent who blindly follows anything someone else says without using their own brain is an idiot.
No book/theory is 100% perfect and works 100% of the time for 100% of babies. Don't use a few obvious mess ups (Houdini strap) to rubbish the rest of it.
Ps I like your analogy of modern and cave baby. I have this vision in my heads of the bubbas in cute little Flinstones outfits