> Personally I'm of the opinion that you can get really far knowing C and Common Lisp.

Yup. I advocate a fast running & low level language like C plus a quick to get started with lots of libraries language like Python.

At the end of the day, unless pure algorithms are the deliverables (and it may very well be), it is really about the libraries and ecosystem. In the majority of cases, it is simplest to re-use code someone already wrote. Who cares if this language compiles to assembler and is super functional and does all kinds of fancy tricks, can it read from Postgres or talk to RabbitMQ? Does it have an easy way to parse JSON or generate uuid's, or do I have to now spend time writing db drivers, json parsers before even starting on the real problem?