I'm going to have to disagree with you, especially in relation to large frameworks.
I spend a lot of time working with medium to large ruby on rails applications. I know them very well and I am pretty good at doing things quickly and correctly. If I have to work on a php, python, or javascript project, it takes me one or two orders of magnitude longer to get things done than it would in a rails application.
The ability to start working with a new language after reading a blog is useful but it doesn't mean you'll be effective and useful in that language in a week.
I spend a lot of time working with medium to large ruby on rails applications. I know them very well and I am pretty good at doing things quickly and correctly. If I have to work on a php, python, or javascript project, it takes me one or two orders of magnitude longer to get things done than it would in a rails application.
The ability to start working with a new language after reading a blog is useful but it doesn't mean you'll be effective and useful in that language in a week.