It gets easier

[Motions]

I think you might be reading the graph slightly wrong.

From https://community.wanikani.com/t/my-journey-of-368-days-the-ultimate-guide-for-wk/31318/2 where I found this:

@jprspereira

This graphic assumes 100% accuracy and the y-axis represents not your daily workload, but the total number of items in various stages of learning (burned excluded). It’s not perfect, but it does a good job in conveying the reality that Wanikani is in my opinion