Each time a discussion on the question "Is Ruby/Rails still relevant in [this year]" comes up around here, an answer to the effect of "Ruby/Rails is still the fastest way to go from zero to working prototype/product" ranks highly.

Python and Javascript have different standout attributes but it comes back to the same key point: most people building regular apps/sites/products care primarily about building something functional as fast as possible.

It would make sense that productivity would be a primary concern in the earlier stages when it's not yet known whether a product idea is viable.

But type safety might become a consideration later as the development team becomes bigger, the codebase becomes more complex, and production reliability becomes an important consideration.