I think I’ve had a lot of the same thoughts as OP here as well. I’m on a church service mission where I have quite a bit of time, and during my less-motivated times on WK I’ve thought “I have so many leeches and I don’t level up nearly as often as I mean to, is this unacceptably slow?” And I think the answer really depends on the person. I tend to do 10-20 vocab every night and do the kanji all at once. That’s far too fast for some people and far too slow for some others, but it’s working for me right now (assuming I don’t get burned out…like I did at times heh)
To OP I would say, are you going as fast as you would like? Sometimes I think it’s important to push through and get through reviews anyway, running solely on willpower. On the other hand, are you enjoying studying and reviewing? Sometimes it’s good to slow down and focus on enjoying study. Noticing your progress and how you learn are as important (or, I think,
more important) than whatever you perceive that other people think a reasonable levelup time is. Even if you took a decade to do Wanikani, if you enjoyed doing it and the knowledge you gained, and it was worth the money, that would be worth it in my opinion.
But take it at whatever your own pace is! We’ll welcome you here no matter what, and no matter how fast you learn, choosing to continue learning and reviewing means that you’ve already won!