... Because I want to be able to do that WITHIN my webapp?
As a side note, I wish this guy would of pointed to some specific examples instead of speaking in generalities.
It is very hard to give specific examples, most this kind of blog posts are mostly rants without anything concrete to grasp on. I guess it's mostly about what kind of coding/architectural style are you used to.
For example, I have done rails several years ago. I liked it, but just couple of small projects. Then I started my next site with django, which I liked very much. I found the django's modular system much better than rails, and it was very easy to add functionality through open-source packages and customize them for my needs.
Now I have started contracting project where I fix existing rails project, and it is kind of pain in the ass, because I'm used to django's way of thinking. But I can't give any specific reasons why it sucks, it is just my viewpoint.