Damith, as a developer for 40+ years, I think you are wrong.. No, a Web developer does not need to understand the intimate details of the HTTP protocol, but he does need to understand its behaviors, its strengths and limitations, and how to use it to advantage.

Learning to superficially use something without learning it puts one in a precarious position when one hits an edge-case failure and has no clue how to analyze and fix it.

On of my personal irritations is the Web developer who only knows how to use a framework like Angular or React, but has no clue about the commonly accepted principles of UX. There are too many applications out there that are needlessly hard to use and error prone. Fitness for purpose is a legitimate competitive factor.