WaniKani is good for structure. You get a program (starting with the visually simplest kanji) and go through it, level by level. The tradeoff is speed and flexibility. You don’t get to skip levels or suspend leeches.
@Naphthalene is one example of someone who started using WK with a lot of JP knowledge already, went through all the levels and wrote a Level 60 post where they recommended using WK. [Review] Making it to level 60 as an advanced Japanese learner
Meanwhile, @Vanilla the speed demon he is, did not possess as much JP knowledge went through WK and seems to regret it for how slow it was. My Complete Journey, Reflection, and Advice for Achieving a High Reading Level in Japanese
So people are very different in what they consider the benefits and whether that makes it worth it to use WK.