This question gets asked all the time. I think it could be clearer, but I also think new users should be aware of what they’re signing up for. Reviews are definitely not optional on WaniKani; they are really the core of the site.
I have answered this sort of question a few times before, so here’s a link to one of my previous answers (to build on previous posts in this thread): Still unsure how to use the app - #3 by northpilot