Take a look at how fast javascript mutates, I'd argue that rate of mutation is one of the things you can do in a dynamically typed language. Java doesn't mutate like that, despite having many of the same ecosystem pressures, such as the pressure to "be good at everything" because it's so widely used.
That mutation often comes with unneeded parts and kludges, but the rate of mutation and change in the JS ecosystem has also been a huge positive. Still, TANSTAAFL and all that, I'm certainly not saying it's all good -- but I think you overstate it considerably when you say "A lot to lose and nothing to gain with dynamic typing"
