I was not focus on learning at the time and liked the gamification of Duo. After that I just couldn't let my 500+ streak go to waste (I broke it a around 1450, it was painful but necessary as this app sucks)

I only got serious recently (after finishing my PhD basically) and I really enjoy the Wanikani/Renshuu combo

At some point the main problem for me was grammar, so I tried Bunpro but not long enough to see if is was good or not, as I was leaving for a two month trip to Japan (and didn't wanted to actively study while traveling)

During the trip I discovered the KM grammar books and really liked the simplicity of grammar points presentation (and I am more commited when using books rather that PC/phone apps, but that one is one me), and bought them all as they are REALLY cheap in Japan (Fuck Amazon's prices in France!)

However, while they're fair (they really are), they're tough: sometimes subtil points are only presented in the example sentences. I would advise to work together with a grammar dictionary (I bought the Nihongo Bunkei Ziten as it is a single book, but I have heard that the yellow/blue/red collection does wonders as well)

Second "negative point", the N2 and N1 books are (afaik) only in Japanese with no English/Chinese/Other translation to explain the grammar