My understanding of Argo CD is limited so forgive me but I believe Koreo is a bit more similar to Argo Workflows. Where the scripts and logic is baked into the Argo Workflow image, in Koreo it leverages other K8s controllers to do the heavy lifting of interacting with the APIs. If I understand Argo CD correctly, it is an implementation of Argo Workflows. In this way, you are able to build your own CI/CD workflow via Koreo if you so wanted.

Where Koreo excels is when your developer knowledge ends with a Dockerfile and your platform team is able to abstract service deployment away from them. Many organizations use a "god chart" to do such a thing but those will become cumbersome over time. Koreo's value prop also is greatly enhanced when paired with ACK or Config Connector as you have an organization specific DSL that will integrate your container runtime with your cloud resources. E.g. mount your rds address on your pod in one workflow.