> If an LLM can teach me a language, why wouldn't I go straight to the source and use GPT or Claude and customize it to my exact needs.
Because the "customize it" part is not trivial. That is the value add for most people who can not do that customisation themselves.
That said, I've found LLMs to be terrific if the goal is to learn the rules of language's grammar. But to actually learn to speak the language, find HelloTalk to be best, beaten by nothing other than actually sitting down with a native speaker.
Duolingo does not need a moat. They are already an established incumbent and have market inertia on their side. They can afford to experiment and make mistakes, and then to backtrack those mistakes.
For what it's worth, I also stopped using Duolingo when the human forums closed. I often found as much value in the forums as in the actual course. And like GP, the hardest part was relinquishing my nearly 1000 day streak.
I'd love to see someone build Duolingo with a single system prompt. By HN standards, no one would be paying for Character.ai, Cursor, Windsurf, or dozens of others tools because they could just call the ChatGPT API themselves.
That said, I've found LLMs to be terrific if the goal is to learn the rules of language's grammar. But to actually learn to speak the language, find HelloTalk to be best, beaten by nothing other than actually sitting down with a native speaker.