I did both the Spanish and French trees completely, I do think I learned some things along the way, and some of it stuck. Every language learning method is not perfect, you need to immerse with multiple things. I was living in country, doing duolingo, listening to pimsleur, listening to radio in language, going to classes and hanging out with native speakers, and my fluency still is not great. It takes years of being a child before you get anywhere and no system is going to solve it alone