It’s financially motivated which is frustrating for some people and much less polished than Duolingo from a ui perspective but at least for Japanese (the only language I practice) the courses make much more sense and are more challenging

The only advantage Duolingo has over it really is the ability to practice stroke order for kanji/hiragana/katakana but if you’re not learning Chinese/japanese that’s not really an issue. Lingodeer will still teach you the characters, just not how to write them. And lingodeer integrates writing with the characters far earlier, basically at lesson 1, which is challenging but helpful. Vs Duolingo which makes this entirely optional so you can complete the entire course writing in “romaji”/latin script for Japanese (eg “konnichiwa” instead of こんにちは. And even if you use hiragana you can use that entirely and never use kanji (eg わたし instead of 私 for watashi)

It’s because Duolingo is overly focused on gameification. They artificially make things easier so you progress at all costs even if that means you are overall forming worse habits and learning less. On one hand this is more likely to keep you motivated, on the other it’s more likely to sell subscriptions, keep engagement in the app up, and sell iap items to manipulate the iap system. Then they can portray it as altruistic (“we are keeping you motivated”) when it’s really compromising your education to raise profitability. Yuck