Earlier quoted context omitted.
Generally speaking, a UI DOES have a use case - when you can't be bothered to learn the configuration language and its keys / values / nuances. The UI can help you create a sane and safe config, instead of having to scour the internet for - potentially outdated - information. Mind you, I've had more trouble with that with Apache given how they changed their config files around on multiple occasions.
I'd argue that if you are neither willing nor able to learn nginx's config file format, you should not be configuring nginx. The default config has example blocks with comments anyway. If that's not enough, nginx maintains current documentation. But if you're configuring a web server (or anything, for that matter), you should take some time to learn how to configure it.
Have we already forgotten how Microsoft Exchange singlehandedly launched an entire spam industry?