That's the point, isn't it? It takes these dark patterns that predatory game devs/actual gambling apps have been researching and minmaxing for years and points

That's the point, isn't it? It takes these dark patterns that predatory game devs/actual gambling apps have been researching and minmaxing for years and points them at something useful and productive instead (language learning). The result is a language learning app with very effective user retention and repetition, which is especially useful for a subject that requires lots of repetitive practice. As far as I can tell there isn't any actual gambling and the microtransactions/lootboxes appear to be simulated and don't depend on actual money. This overall doesn't seem like a bad system to me. I think their overt dark patterns are intentional and are tripping your "this is malicious" sense when in fact I would give them kudos for using them in a way that is beneficial to people.