What are the long-term benefits for kids to learn coding? Will kids really be left behind without it?

The biggest benefit is gaining a fundamental understanding of how technology and software work. We learnt physics and chemistry in school not because we were going to be scientists, but because we needed to have a basic understanding of how the universe works. The universe our kids live in today runs largely on tech. Learning coding (or more generically computer science) is learning how the digital world works and learning to use computational thinking to solve problems.