Each task has it's set or preferred tools, to write a quick command line tool to bridge a gap between two systems and automate our workflow a bit further python is just perfect for me and much more productive than C#. However to create a system with a team of dozens spanning the whole skill gamut I feel much more comfortable having the compiler as an active member of my team policing the architectural vision for us. In which case C#/Java will win hands down.

If however speed and responsiveness are prime worries then I'll roll up my sleeves and bring C/C++ in. sure my productivity will take a hit, it will likely be harder to maintain as well but if this effort makes the difference for my customers in their productivity then it's well worth the investment.

Often times the final system will be a mix of all these technologies, each used where it's strength shines to maximise their impact.

Yet the technology is worthless when faced with inadequate code structure and system architecture. Coupled convoluted code will be a PITA no matter the language used.

Couldn't that be solved with sane variable naming conventions and docstrings/documentation?

That is not where productivity sinks are. They're in build systems, package managers, existence of good libraries and ease of debugging as well as limiting number of accidents while coding.

    dynamic f = x => x * 2;