Plurals, Definite Articles and more
When the Korean course first came out, I was a Korean living abroad with English as a first language. Obviously I was quite excited for the course, as I could learn much more effectively. I really liked the way it handled the honorifics system and the one skill for the Pyeongchang Winter Olympics - but I couldn't help being frustrated at some points.
Firstly, in Korean, the plural does not necessarily have to be included. 감자가 먹어요 can mean there is one potato or more than one. But in the courses, it is marked as wrong if you deviate, even in cases where both are completely acceptable.
Then, the definite articles. Korean, like many languages, doesn't have them. But again, the course sometimes only marks an indefinite or definite article as correct. This forces you to learn which one the course wants, instead of actually useful stuff such as vocabulary.
Next, the personal pronouns. The problem is the constant usage of them in a language where they can be left out. In Korean, they're used like italics: to emphasize. But translations don't accept them, again making you memorize if a particular sentence used them or not.
And sort of continuing this, there are far too many set translations and expressions for my like. Yes, of course Korean has them. But the thing is that Korean and English are completely different. Many words have multiple translations. Saying 선수 only means 'player' is like saying 'train' is exclusively a verb. .
Of course, the course is still quite new, and will only get better. But this stuff is really quite important. Plurals, definite articles, personal pronouns and flexible translations are all quite basic elements of language learning, and key to having conversations in Korean, especially with native speakers. And for those who had been learning Korean beforehand (such as me), it creates a headache.
Besides my comment on your other post (where I did not address any specifics), I agree with many of the points here regarding pronouns, articles, etc. If you've done the reverse tree like I did in the past), you'll notice that the present tree is already much more flexible than the former one. Now, very often, especially for lower levels, the pronoun-free answers are already accepted. Yet again, it boils down to do our job as beta testers: provide as many as possible alternative translations.