It’s interesting. Your experience is different from mine. I find KaniWani very easy compared to WK. I always assumed it was because I would always go through the WK lessons and reviews before turning to KW, since KW has no influence on my rate of progression through WK. Well, no direct influence, anyway; it certainly indirectly helps me with WK overall, but I just mean that nothing at KW will restrict my progression on WK, whereas there’s absolutely a restriction the other way around.
However, if you’re finding it harder than WK, maybe there’s more to it than that. Off the top of my head, I’m wondering if you’re also studying some grammar? I found that studying grammar on BunPro is a very valuable complement to learning kanji/vocab on WK/KW. In fact, of the three, I find BunPro much more challenging, but it also helps me to recognize both written and spoken Japanese words because it gives me some structure and context to what I’m reading or hearing. Instead of just being able to pick out a word here or there like before, I can now get the ‘gist’ of parts of sentences where I don’t actually know the vocabulary words, but the grammar words and particles give some familiar structure that lets me understand the overall purpose of a sentence, even if I don’t understand the specific content of it.
So, perhaps, if you’re not doing it already, it might be worthwhile to start learning some grammar to complement your vocab/kanji. This might make words easier to recognize; e.g. to distinguish between nouns, verbs, suru verbs, adjectives, adverbs, and the like. It may also give you enough contextual elements at your fingertips to help you ‘produce’ vocab words in context by starting with some grammar words to get the ol’ engine started.
Before I jumped into the WK/KW/BunPro pools, I spent a bit of time working through the Genki books, and some other books (I think Tobira, and maybe another one, but can’t remember). These recommendations I got from Tofugu (the companion blog of WK), and they were good recommendations. I also used Anki for a while in conjunction. But I lost momentum at some point (forget why) and when I came back to learning Japanese, I felt that I needed a bit more ‘hand holding’, so WK and the like were perfect for me at the time.
Point is that I already had some experience learning both vocab and grammar, though not so much with kanji. So, maybe that’s why I find KW pretty easy, comparatively speaking.
And due to the fact that you can go at your own pace on BunPro, not restricted to a certain pace like on WK, I’ve already whizzed through JLPT N5 and N4 on BunPro, and now I’m facing new and thus more challenging grammar there, whereas I’m still finding the vocab level on WK a bit still in the ‘past grade review’ stage for me, though it’s starting to get a bit more challenging as I advance through the levels.
So, to recap, maybe branching out into a complementary aspect of the language (grammar) would help you with giving additional context and experience with the vocab aspect? Just an idea.
Another very helpful resource for understanding Japanese grammar has been Cure Dolly’s grammar videos on YouTube. Her conceptual approach (not original to her, but she does a great job presenting it, IMHO) really helped me get past several stumbling blocks and to get a better understanding of how Japanese actually works.