Wanikani is just not useful enough, but could be

[crihak]

Koichi had this to say about the topic a while back

Brand New and Looking for Advice

Sometimes that’s true, especially for kanji with not many good words, but a majority of the time vocabulary words are chosen because they’re useful or common. Granted, this standard is set for reading and not speaking, though there should be considerable overlap between the two. Also, as our users often remind us, we will forget words too, so please email us if there’s a common / useful word you think ought to be in WK that isn’t. <3

And also in that thread made this comparison with the iknow.jp Core6K/10K word lists floating around

@crihak

As a bit of an aside, I did a bit of checking, and out to the 10000 words in the Core10k deck, this is, by 1000-word batch, how many are covered by WK. Sensibly, this is heavily skewed towards the more common ones:

0000-1000 743
1000-2000 573
2000-3000 403
3000-4000 554
4000-5000 348
5000-6000 279
6000-7000 278
7000-8000 269
8000-9000 219
9000-10000 114
Total: 3780/10000

So, you’ll learn 38% of the 10000 most common words (74% of the 1000 most common).

Conversely, of the 6287 words WK teaches, 60% are contained in the Core10k deck.