Speaking as a total ignorant from a coding perspective. But I guess that wouldn’t be the hard part, considering that most of Duolinguo is just boxes and text inputs. How difficult it is to create a database of competent linguists with an efficient training who can progressively enhance your understanding of languages?
I’ve been learning French on there for awhile now and it’s been extremely effective por moi. They teach you as much French as you would get in a 4 year university program. Plus having an AI powered practice set is like having a teacher who knows exactly what you know and what you need to learn more.
Try taking a break for a month and see how much you actually remember. In my experience it was depressingly little, and I’m not generally bad with languages at all.
I think that would go for most learning methods. When you don’t practice a skill you’re always going to get worse with it over time, especially if it is a language.
After a certain point you should be able to retain a language for more than a month - after you’ve attained B2ish level I’ve heard.