For those who don't know, CSS is a language that gets embedded into web pages that basically can "flexibly skin" a very plain (mostly text) web page into something pretty and image oriented with changing colors, fonts, graphics, text styles, etc.
The apparent dislike of CSS in the Amiga community is from a combination of things, like lack of a lite graphical browser that supports CSS that would work OK on an 020/030 class machine, and the fact that most CSS web page graphics and web browsers implicitly expect to run in a high-color or true-color screen mode with alpha transparency effects, not something limited to 256 color lookup tables in an Amiga AGA or 16 color pens on an ECS bitplane environment. Remapping such imagery can look absolutely horrible to OK depending on how well its done.
The defacto Amiga GUI programming toolkits were also created long before CSS took off in popularity, so they don't directly support the CSS/HTML dynamic design model well.