You should be writing tests for all code - Not just dynamic languages. Compilers catch things like typos and type differences as you said; but there's so much more to test suites than that.
Your last 3 points have nothing to do with the post; they're just essentially more information added to other headings.
So your main point in the end is "Rails is slow" - I personally haven't dug too much into the performance of rails compared to others - But in general: It will improve - as all things do.
You should be writing tests for all code - Not just dynamic languages. Compilers catch things like typos and type differences as you said; but there's so much more to test suites than that.
Your last 3 points have nothing to do with the post; they're just essentially more information added to other headings.
So your main point in the end is "Rails is slow" - I personally haven't dug too much into the performance of rails compared to others - But in general: It will improve - as all things do.