Helm has a much narrower use case. Artifactory can host a wide range of artifacts. For example Artifactory can host and proxy maven, NPM and similar programming language library repositories.
But that's assuming you use Kubernetes.
Helm is not a replacement for Artifactory, I don't know what you're going on about. They have a bit of overlap but the main use case of Artifactory is as a binary artifact repository for any environment, including non-Kubernetes ones. And there are a lot of non-Kubernetes environments out there. I'd argue that Kubernetes environments are a drop in the ocean compared to everything else.