I have spent a lot of effort in Duolingo in multiple languages, that I now use daily. Imo it's a mediocre but _extremely_ convenient way to build a base of vocabulary, but it is completely different to seriously learning a language (unfortunately). As far as I'm aware this applies to all the apps - real human conversation is very hard to usefully simulate.

That doesn't mean Duolingo isn't useful, it's definitely helpful, even if you're living in a full immersion environment, but the map is not the territory. If you really want to learn to talk to people, you have to talk to real people. It is a completely different thing to just learning all the words and grammar, far more than I realised before seriously getting into languages.