I agree and disagree with you. If WaniKani would force you even more into only doing so many lessons at a time, even more users would complain. Because there are those that would like to go even faster and those that feel overwhelmed and punished by getting even more lessons by having successful reviews. So it’s clear that Wanikani had to draw the line somewhere if they wanted a level based product. And I find it also fair that they aren’t as customizable as Anki, but rather have some very clear limits.
But I also don’t understand why they made the demotivating choice to only count Kanji as level relevant items. It’s just as you said; Vocab fills the majority of your time, but also gives the least gratification. It’s the Vocab that stresses your conscience by piling up while hindering you from leveling and therefore entices you to either do it all in one go or ignore it - both with unpleasant consequences.
Furthermore I agree that a bit more customization (instead of endless userscripts) and a bit more guidance really wouldn’t hurt. They tell you practically nothing about the mechanics of their website and how you should use them for your advantage and just a short article about recommended use and how certain rythms (many lessons, few lessons) work should be in the FAQ. They don’t even recommend you to try to get a new Lesson to App 3 in one day; those are all things where you have to make the connection for yourself.
So, while I disagree with some of your demands, just because they fall in the category of “there’ll always be someone who isn’t happy, you can’t serve a whole spectrum of demands”, you’ve talked about some things that properly irritate me as well and where I can’t comprehend the decisions of the staff.