Doesn’t really answer your ask about fixing the difficulty of WK’s example sentences (though I also, since I came to WaniKani after many years of studying Japanese and trying to learn kanji other ways, actually like them as they are), but… to go with @Leebo’s theory of “more is better”, maybe add @psdcon’s [Userscript]: Anime Context Sentences?
I don’t use it myself, but from the descriptions most of those context sentences seem to be on the easier side!