You have to record which ports your applications listen on, which subdomains are used for what, how to access that storage bucket with the data files in it etc. somewhere. The moment you have more than a couple of individual services managing this all by hand becomes a nightmare. You need a really strong culture of good practice to make sure that the exact production config actually ends up in source control.
You can be a k8s expert, or an expert in your own home-spun configuration management/git-ops workflow. But not having any workflow here just isn't an option in my opinion. You too easily end up with spaghetti infrastructure that everybody is too scared to touch. With k8s I can take my repo of yaml and change cloud providers in an afternoon.