The real question is who was still buying this type of book in the last decade or two? What value were they getting out of it? Was it being used as reference or training or what?
Rachel Andrew’s (mentioned in TFA) for example has The New CSS Layout (2017) https://abookapart.com/products/the-new-css-layout.html an excellent book I still recommend for anybody who want to learn about modern CSS layout.
But if you are this dismissive of the field of course you will fail to see the value of them.
I’ve never understood that but for some reason it is a thing