While of course you're correct, it's a bit like saying "you can just pack up your code and run it somewhere else". If the entire architecture and workflow are based around proprietary AWS tools (Elastic Beanstalk, Elastic load balancers, RDS, Cloud Formation, autoscaling, etc) even if your code is technically portable, you're still suffering from vendor lock-in. Arguably worse than the bad old days of the Microsoft monopoly.