Maybe you're not supposed to use just salt?

You can, but you need a high enough concentration to fight off disease causing microbes while still encouraging the interesting microbes (lactic acid bacteria and certain yeasts) that make the distinct flavors of pickling apparent. And you need to work with temperature and time to make sure you don't make the vegetables mushy.

Follow an established sauerkraut/choucroute or kimchi recipe that has already been shown to be safe, rather than trying to wing it on your own. This stuff can make people sick.

The only Japanese thing I know is made by just packing something in salt is soy sauce (which isn't pickling it, it's fermenting). Even pickled cabbage is usually in a brine, you just don't soak it for a long period of time. You rub the cabbage down in salt initially, but then you also would add lemon juice or vinegar to it.