I see it as "this is the official way that the project uses to host, and they have been kind enough to share it with you".

I don't think Zulip themselves use Helm charts or Kubernetes Operators to host their instances. If you think hosting an instance without these is such a pain, why not just pay them to manage it for you? At least you got the option to self-host, which is not something you'll ever get with Slack.