Renshuu provides fantastic SRS based tools for memorizing the hell out of vocabulary, has a huge bank of grammar lessons and a variety of grammar quiz styles to bed in the knowledge through practical applications. There are multiple quiz styles that are more or less challenging, including typing out answers instead of multiple choice questions.

Using just Renshuu and Wanikani I learned enough Japanese to be able to engage with Japanese content and for it to be actually comprehensible.

In the past I tried learning through immersion only, made no progress, found it demotivating and gave up. You need a baseline of vocab and grammar, and I don’t think it matters much where exactly it’s coming from (apps, lessons, textbooks).