Sometimes a solution that is specific and targeted is more efficient and usable than a general solution molded to fit the problem.

No one says that if you need a relational database you should reimplement it yourself - just that the DB is not the only solution for all web back ends.

Yep. No matter how you phrase it, there are people out there who will never see how that might be true. I've said before that using the file system or caching data in memory isn't an anti-database technique, it's simply a solution to a specific problem. It won't matter though - someone will have a fundamental issue with the approach, no matter how you present it. That's life.

_molded to fit the problem_

Most problems I've worked on had to take scaling, concurrency, searching/lookup, report generation (joining), etc, into account...all of which a dbms gives you out of the box. Maybe we're dealing with _very_ different kinds of problems.