That is AS400 from IBM. Although discounted by IBM, it is still in production in many places running mission-critical apps. It's far better than the stuff people write today. This is how reliability looks. Why break it when it works?
@nixCraft True, and it's going to become worse! Now we have hard to maintain agile JS codebases. In the near future we will have impossible to maintain agile JS codebases written using fabulating AI bullshitters.