This has been my experience that in the long run everything else is a distant second to vocab acquisition. I think even within vocab the long tail you have to worry about is overwhelmingly nouns. Verbs are also numerous but can often be inferred from context, replaced by simpler verbs etc. 95% of the time when I’m watching tv news and can’t follow its because they use some finance, politics, medical terms etc that cannot be guessed. There are simply far more ideas/things in the world than anything else. Unfortunately the truth that language learning is a long slow grind to learn nouns doesn’t fit well with those who want to make it a more intellectual exercise or other pedagogical goals of academic settings.