Nowadays, complex applications are written combining several language. For example google uses C++ and Python to take care of search engine related stuff, and use Java and Kotlin to optimize performance for android user. Apart from that they also use a dozen of language for other tasks.
A machine still needs JVM to run Java code.
You probably don't have much idea about automated testing. Testing isn't generally manual these days.
The language is not that important. Python has tons of data analysis and ML libraries. That makes it useful for Big Data and Machine Learning tasks. But in the end, most important thing is to have good idea about concepts like regressions, clustering and different algorithms.