The language I was learning had no tuition available for adults in my country and I practiced with native speakers when I could find them and consumed media from the community of the target language.
All while on public transport, when I would otherwise be on my phone. All for the price of nothing (though their model has grow much more user hostile).
This is not to advocate for Duolingo as a company or even the app as a method but I found it effective and useful as a tool.
Duolingo isn’t going to learn a language for you. You have to internalise the grammar and vocabulary.
Could I have done the same with a book? No. I could have done something different. Could I have done the same with a class? No, no classes existed for me.