CDK8S doesn't replace Elastic Beanstalk, because the folks using EB are going to continue to use EB. If it ain't broke...

ECS predates EKS, and is better integrated than EKS with their other services. If you want a painless container experience on AWS, ECS for Fargate is what'll you'll want to use today. So both existing folks who use ECS today as well as new customers are going to keep using ECS.

Folks who like K8, perhaps from prior experience, are going to use EKS despite it having some rough corners.

See, Amazon is perfectly happy to support everything under the sun as long as there are paying users. See their database offering for very much the same strategy, and it would be silly to say that they should drop DB x since they now offer DB y.