But that's not a cloud provider thing, that's just the same-old locking yourself into proprietary software that we've been doing since computers were first invented. "We have to renew the license on our Fortran compiler because nothing else has the features we use" is exactly the same "I'm stuck on DynamoDB".
As for Ingress, Amazon does have an ingress controller that configures an Application Load Balancer with kubernetes Ingress API objects. I feel like this locks you in less because again, Ingress is standardized. The problem with Ingress specifically is that the standard doesn't cover things people actually want their ingress controller to do, so every implementation has their own set of features. We use nginx... you better believe there are literal nginx.conf snippets inside the Kubernetes API objects to get things to do what we want. So this is just a case of Kubernetes being bad, not really cloud provider lockin. I'm more stuck on nginx than on Amazon.
(As for load balancers; again, Amazon has proprietary configuration parameters that won't be portable, but they don't really do anything important. You can make your Amazon load balancer terminate TLS (a bad idea), and pick which of the 3 Amazon load balancer types you want to use.
Switch to Google, and that won't work... but you also probably won't care. The Load Balancer API spec seems to do what people want, so it's relatively commoditized and you won't be sad when you switch providers. We actually have to have a wildcard certificate specifically because Amazon's classic load balancers are so bad. Would be happy to not terminate TLS in the load balancer and have Envoy or Nginx terminate TLS and ask letsencrypt for a new certificate every couple months.)