You're not considering how scalable your simplified solution is to a team of 100+ people developing the same codebase.

Most of the problems of software engineering are not technical, they are social. Web development is simple for a team of 1-10. I love the idea of hand-writing CSS and relying on simple scripts for myself and a few teammates. Unfortunately it doesn't scale to large orgs.

It's not that people don't want to learn.