> Twitter's back-end is written in Scala, but they used "better Java" style so an average developer should have no problems making changes
You sound like someone completely oblivious to software development practices who somehow felt compelled to post opinions on software engineering.
Your choice of language is irrelevant if your goal is to maintain software. What matters is systems architecture and institutional knowledge of how things are designed to work. If you fire your staff, you lose institutional knowledge. Your choice of programming language does not bring it back.
You sound like someone completely oblivious to software development practices who somehow felt compelled to post opinions on software engineering.
Your choice of language is irrelevant if your goal is to maintain software. What matters is systems architecture and institutional knowledge of how things are designed to work. If you fire your staff, you lose institutional knowledge. Your choice of programming language does not bring it back.