A typical app can be made pretty reliable with enough testing effort and a good process, so I'm not surprised that large apps have been written in dynamically typed languages, although I am now curious which apps you had in mind. Can't think of anything the scale of e.g. Photoshop, Oracle or Linux.
Re STL: Really? :) I'll take missing hash-tables (dictionaries are fine) any day over no library. I don't know which period you're referring to with the ifdef hell, but at least for the past decade I can't think of any STL compatibility issues. Perhaps you can be more specific here? In any case, JS never had such issues because back then it was being used to make text blink. Now that it's facing more challenges we start seeing the issues.
Re working on browsers: you're not a web developer. I will say though that Mozilla pushing this web-everything agenda is disappointing. The FirefoxOS lesson has not been learned...
There have been tons of reliable large apps written in dynamically typed languages. This is, again, a tiresome argument.
> the STL is currently working great! JS would kill to have something as stable and high quality as the STL.
The STL took nearly a decade to get hash tables. And for years, users suffered from Microsoft and other vendors taking very different approaches to template expansion, causing no end of ifdef hell. JS never had such issues.
> But that doesn't scale when building widgets and doing positioning.
Huh? How does flexbox "not scale"? Positioning is just one aspect of style.
> At one point web developers need to talk less and deliver
I've been working on browsers for 7 years, and on most of those weekends, thanks.