Self-taught is a double edged sword.
It generally can't occur without some level of passion for the material. But you also tend to miss the boring details.
I did full CS / Software Engineering curriculum. There was a lot that I taught myself because I was curious / passionate. I learned a lot about things not covered in classes. But the classes also taught the boring details of things like data structures that you can generally ignore until you hit some level of scale/success.
I've seen self-taught software engineers build great looking UIs and during the code review point out things like "data structure X" would work better. I get a response about "Premature Optimization," when in fact the right data structure would be less code and I have to show them.
I've also met self-taught engineers who read detailed research papers on topics on and sometimes made things perhaps more complicated than they ever needed to be.
passion & formal education definitely play interesting roles in what people produce.
I spent 8 years in jr high - college studying German without having any real competency in German, it did however teach me something about learning another language.
Mango isn't gamified. Its basically a curated set of flashcards, and the lessons are essentially flashcards themed together. There are some extra explainers throw in that are helpful. I really enjoyed it.
On top of Mango as the primary lessons, I've been listening to podcasts, watching series in french, reading books, etc.
I didn't pay anything for mango, it was entirely funded by my local library so that was great.