I wouldn't say you're missing out. If kustomize works for you, keep using it. I personally use helm because I cannot for the life of me wrap my head around kustomize. I've looked at tutorials, read the docs, and it just doesn't make sense to me. Helm, on the other hand, immediately clicked and I was able to pretty effortlessly write charts for our use. It's just a case of different preference in tools, imo.