I agree with many of your points, such as understanding how the lower layers (HTTP, SQL) work.
But not using a framework will cause a lot of headaches. Writing code for a toy website is one thing, but writing one that supports real users and customers is another thing. No developer would want to write original code for SSL, user authentication, a templating tool, all those HTTP headers, a caching module, session handling, a custom ORM, etc.. Writing original code for authentication alone would be extremely risky and prone to security flaws.
I "get it" that developers need to understand what's under the hood. They should have CS fundamentals down. But not using a framework and trying to write all new code for a website is a bad idea for 99% of projects.
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