There are two pillars to success when learning any language: vocabulary and grammar.
The thing about them is, they are actually rather orthogonal to each other. Even in Japanese, as long as you learn the dictionary form (or to some degree even the polite form of the word) you don’t need to worry too much about how to use it to know the word.
You need to know both, obviously, but you can work on both separately, and not lose anything when it comes to learning whatever language you’re trying to learn. Eventually, of course, you have to tie them together, but that actually happens rather naturally with exposure.
And each requires a separate way of learning. Vocabulary seems to work best through a combination of exposure and rote memorization, but grammar seems to work best mostly through exposure and immersion. Grammar is how you learn to think in a language, and vocabulary is how you learn to express the thoughts within the framework grammar teaches you.
I think this is one reason why Japanese is seen as so difficult: in order to learn either vocabulary or grammar, you first need to learn the framework in which both of those things are expressed. Such as hiragana, katakana, kanji, particles, etc. And you have to learn them before you can move on.
That’s the “hump” I was talking about earlier. Japanese is very much not an instant gratification language, if you’re starting from zero.